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	$74.88	6.454%	$79.7128	$79.71	$79.70	$79.70
Purchase #2	$223.34	11.449%	$248.9102	$248.91	$248.90	$248.90
Purchase #3	$20.88	7.840%	$22.517	$22.52	$22.50	$22.50
Purchase #4	$164.88	13.780%	$187.6005	$187.60	$187.60	$187.60
Purchase #5	$135.61	8.769%	$147.5016	$147.50	$147.50	$147.50
Purchase #6	$235.92	7.816%	$254.3595	$254.36	$254.35	$254.40
Purchase #7	$111.76	7.300%	$119.9185	$119.92	$119.90	$119.90
7 purchase totals =	$967.27		$1,060.5201	$1,060.52	$1,060.45	$1,060.50