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	$70.73	10.399%	$78.0852	$78.09	$78.10	$78.10
Purchase #2	$86.72	8.664%	$94.2334	$94.23	$94.25	$94.20
Purchase #3	$235.42	4.567%	$246.1716	$246.17	$246.15	$246.20
Purchase #4	$99.46	5.629%	$105.0586	$105.06	$105.05	$105.10
Purchase #5	$160.66	4.680%	$168.1789	$168.18	$168.20	$168.20
Purchase #6	$205.79	7.734%	$221.7058	$221.71	$221.70	$221.70
Purchase #7	$162.58	4.251%	$169.4913	$169.49	$169.50	$169.50
7 purchase totals =	$1,021.36		$1,082.9248	$1,082.93	$1,082.95	$1,083.00