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	$82.47	8.816%	$89.7406	$89.74	$89.75	$89.70
Purchase #2	$48.38	11.397%	$53.8939	$53.89	$53.90	$53.90
Purchase #3	$236.33	5.131%	$248.4561	$248.46	$248.45	$248.50
Purchase #4	$182.98	6.119%	$194.1765	$194.18	$194.20	$194.20
Purchase #5	$237.40	9.499%	$259.9506	$259.95	$259.95	$260.00
Purchase #6	$235.33	4.422%	$245.7363	$245.74	$245.75	$245.70
Purchase #7	$12.34	11.477%	$13.7563	$13.76	$13.75	$13.80
7 purchase totals =	$1,035.23		$1,105.7103	$1,105.72	$1,105.75	$1,105.80