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	$104.42	7.558%	$112.3121	$112.31	$112.30	$112.30
Purchase #2	$99.43	10.573%	$109.9427	$109.94	$109.95	$109.90
Purchase #3	$112.62	13.422%	$127.7359	$127.74	$127.75	$127.70
Purchase #4	$223.92	13.317%	$253.7394	$253.74	$253.75	$253.70
Purchase #5	$108.64	9.841%	$119.3313	$119.33	$119.35	$119.30
Purchase #6	$226.37	6.449%	$240.9686	$240.97	$240.95	$241.00
Purchase #7	$240.63	7.408%	$258.4559	$258.46	$258.45	$258.50
7 purchase totals =	$1,116.03		$1,222.4859	$1,222.49	$1,222.50	$1,222.40