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	$153.33	10.783%	$169.8636	$169.86	$169.85	$169.90
Purchase #2	$50.44	3.311%	$52.1101	$52.11	$52.10	$52.10
Purchase #3	$51.82	5.854%	$54.8535	$54.85	$54.85	$54.90
Purchase #4	$57.83	3.254%	$59.7118	$59.71	$59.70	$59.70
Purchase #5	$105.52	6.519%	$112.3988	$112.40	$112.40	$112.40
Purchase #6	$14.67	11.599%	$16.3716	$16.37	$16.35	$16.40
Purchase #7	$231.59	5.140%	$243.4937	$243.49	$243.50	$243.50
7 purchase totals =	$665.20		$708.8031	$708.79	$708.75	$708.90