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	$191.37	6.743%	$204.2741	$204.27	$204.25	$204.30
Purchase #2	$240.66	7.776%	$259.3737	$259.37	$259.35	$259.40
Purchase #3	$99.77	11.465%	$111.2086	$111.21	$111.20	$111.20
Purchase #4	$174.37	12.581%	$196.3075	$196.31	$196.30	$196.30
Purchase #5	$32.99	11.806%	$36.8848	$36.88	$36.90	$36.90
Purchase #6	$172.64	3.282%	$178.306	$178.31	$178.30	$178.30
Purchase #7	$65.76	4.566%	$68.7626	$68.76	$68.75	$68.80
7 purchase totals =	$977.56		$1,055.1173	$1,055.11	$1,055.05	$1,055.20