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	$233.33	8.793%	$253.8467	$253.85	$253.85	$253.80
Purchase #2	$26.65	8.407%	$28.8905	$28.89	$28.90	$28.90
Purchase #3	$52.68	10.269%	$58.0897	$58.09	$58.10	$58.10
Purchase #4	$89.65	10.410%	$98.9826	$98.98	$99.00	$99.00
Purchase #5	$159.45	4.352%	$166.3893	$166.39	$166.40	$166.40
Purchase #6	$60.65	6.338%	$64.494	$64.49	$64.50	$64.50
Purchase #7	$57.51	4.170%	$59.9082	$59.91	$59.90	$59.90
7 purchase totals =	$679.92		$730.6010	$730.60	$730.65	$730.60