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	$74.58	5.874%	$78.9608	$78.96	$78.95	$79.00
Purchase #2	$12.46	9.789%	$13.6797	$13.68	$13.70	$13.70
Purchase #3	$53.28	11.602%	$59.4615	$59.46	$59.45	$59.50
Purchase #4	$188.59	13.760%	$214.54	$214.54	$214.55	$214.50
Purchase #5	$72.95	4.707%	$76.3838	$76.38	$76.40	$76.40
Purchase #6	$120.63	6.207%	$128.1175	$128.12	$128.10	$128.10
Purchase #7	$127.32	11.472%	$141.9262	$141.93	$141.95	$141.90
7 purchase totals =	$649.81		$713.0695	$713.07	$713.10	$713.10