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	$32.75	3.559%	$33.9156	$33.92	$33.90	$33.90
Purchase #2	$128.78	9.788%	$141.385	$141.39	$141.40	$141.40
Purchase #3	$111.27	6.221%	$118.1921	$118.19	$118.20	$118.20
Purchase #4	$9.61	6.352%	$10.2204	$10.22	$10.20	$10.20
Purchase #5	$151.37	10.279%	$166.9293	$166.93	$166.95	$166.90
Purchase #6	$28.52	13.626%	$32.4061	$32.41	$32.40	$32.40
Purchase #7	$242.87	11.337%	$270.4042	$270.40	$270.40	$270.40
7 purchase totals =	$705.17		$773.4527	$773.46	$773.45	$773.40