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	$53.77	7.494%	$57.7995	$57.80	$57.80	$57.80
Purchase #2	$225.72	3.494%	$233.6067	$233.61	$233.60	$233.60
Purchase #3	$244.27	8.668%	$265.4433	$265.44	$265.45	$265.40
Purchase #4	$204.85	8.664%	$222.5982	$222.60	$222.60	$222.60
Purchase #5	$187.33	11.414%	$208.7118	$208.71	$208.70	$208.70
Purchase #6	$145.76	6.873%	$155.7781	$155.78	$155.80	$155.80
Purchase #7	$29.36	12.186%	$32.9378	$32.94	$32.95	$32.90
7 purchase totals =	$1,091.06		$1,176.8754	$1,176.88	$1,176.90	$1,176.80