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	$92.64	3.502%	$95.8843	$95.88	$95.90	$95.90
Purchase #2	$232.37	7.674%	$250.2021	$250.20	$250.20	$250.20
Purchase #3	$125.48	8.636%	$136.3165	$136.32	$136.30	$136.30
Purchase #4	$95.78	9.219%	$104.61	$104.61	$104.60	$104.60
Purchase #5	$16.61	9.398%	$18.171	$18.17	$18.15	$18.20
Purchase #6	$211.47	10.626%	$233.9408	$233.94	$233.95	$233.90
Purchase #7	$41.63	4.726%	$43.5974	$43.60	$43.60	$43.60
7 purchase totals =	$815.98		$882.7221	$882.72	$882.70	$882.70