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	$200.89	13.348%	$227.7048	$227.70	$227.70	$227.70
Purchase #2	$147.52	12.708%	$166.2668	$166.27	$166.25	$166.30
Purchase #3	$131.33	6.501%	$139.8678	$139.87	$139.85	$139.90
Purchase #4	$42.97	7.573%	$46.2241	$46.22	$46.20	$46.20
Purchase #5	$98.54	7.734%	$106.1611	$106.16	$106.15	$106.20
Purchase #6	$163.48	13.326%	$185.2653	$185.27	$185.25	$185.30
Purchase #7	$127.96	3.688%	$132.6792	$132.68	$132.70	$132.70
7 purchase totals =	$912.69		$1,004.1691	$1,004.17	$1,004.10	$1,004.30