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	$176.96	11.298%	$196.9529	$196.95	$196.95	$197.00
Purchase #2	$109.78	4.559%	$114.7849	$114.78	$114.80	$114.80
Purchase #3	$54.52	13.387%	$61.8186	$61.82	$61.80	$61.80
Purchase #4	$6.86	7.121%	$7.3485	$7.35	$7.35	$7.30
Purchase #5	$231.91	7.320%	$248.8858	$248.89	$248.90	$248.90
Purchase #6	$107.48	10.695%	$118.975	$118.98	$119.00	$119.00
Purchase #7	$69.27	5.548%	$73.1131	$73.11	$73.10	$73.10
7 purchase totals =	$756.78		$821.8788	$821.88	$821.90	$821.90