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	$93.89	10.525%	$103.7719	$103.77	$103.75	$103.80
Purchase #2	$6.58	8.476%	$7.1377	$7.14	$7.15	$7.10
Purchase #3	$242.85	10.753%	$268.9637	$268.96	$268.95	$269.00
Purchase #4	$153.89	8.767%	$167.3815	$167.38	$167.40	$167.40
Purchase #5	$52.60	8.166%	$56.8953	$56.90	$56.90	$56.90
Purchase #6	$50.51	12.821%	$56.9859	$56.99	$57.00	$57.00
Purchase #7	$124.57	11.722%	$139.1721	$139.17	$139.15	$139.20
7 purchase totals =	$724.89		$800.3081	$800.31	$800.30	$800.40