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	$100.69	13.604%	$114.3879	$114.39	$114.40	$114.40
Purchase #2	$146.27	3.243%	$151.0135	$151.01	$151.00	$151.00
Purchase #3	$157.49	4.205%	$164.1125	$164.11	$164.10	$164.10
Purchase #4	$39.72	4.639%	$41.5626	$41.56	$41.55	$41.60
Purchase #5	$34.40	11.404%	$38.323	$38.32	$38.30	$38.30
Purchase #6	$20.92	4.474%	$21.856	$21.86	$21.85	$21.90
Purchase #7	$196.51	6.683%	$209.6428	$209.64	$209.65	$209.60
7 purchase totals =	$696.00		$740.8983	$740.89	$740.85	$740.90