Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$125.92	13.285%	$142.6485	$142.65	$142.65	$142.60
Purchase #2	$197.42	12.534%	$222.1646	$222.16	$222.15	$222.20
Purchase #3	$176.92	10.832%	$196.084	$196.08	$196.10	$196.10
Purchase #4	$176.73	6.713%	$188.5939	$188.59	$188.60	$188.60
Purchase #5	$98.46	7.191%	$105.5403	$105.54	$105.55	$105.50
Purchase #6	$211.73	12.635%	$238.4821	$238.48	$238.50	$238.50
Purchase #7	$135.52	11.413%	$150.9869	$150.99	$151.00	$151.00
7 purchase totals =	$1,122.70		$1,244.5003	$1,244.49	$1,244.55	$1,244.50