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	$143.59	3.397%	$148.4678	$148.47	$148.45	$148.50
Purchase #2	$192.76	6.622%	$205.5246	$205.52	$205.50	$205.50
Purchase #3	$53.78	8.322%	$58.2556	$58.26	$58.25	$58.30
Purchase #4	$129.56	13.218%	$146.6852	$146.69	$146.70	$146.70
Purchase #5	$140.48	8.815%	$152.8633	$152.86	$152.85	$152.90
Purchase #6	$89.36	6.632%	$95.2864	$95.29	$95.30	$95.30
Purchase #7	$47.42	5.652%	$50.1002	$50.10	$50.10	$50.10
7 purchase totals =	$796.95		$857.1831	$857.19	$857.15	$857.30