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	$38.76	7.102%	$41.5127	$41.51	$41.50	$41.50
Purchase #2	$165.49	4.519%	$172.9685	$172.97	$172.95	$173.00
Purchase #3	$167.72	3.846%	$174.1705	$174.17	$174.15	$174.20
Purchase #4	$135.42	12.459%	$152.292	$152.29	$152.30	$152.30
Purchase #5	$244.77	7.696%	$263.6075	$263.61	$263.60	$263.60
Purchase #6	$58.28	5.300%	$61.3688	$61.37	$61.35	$61.40
Purchase #7	$224.97	5.436%	$237.1994	$237.20	$237.20	$237.20
7 purchase totals =	$1,035.41		$1,103.1194	$1,103.12	$1,103.05	$1,103.20