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	$51.93	3.618%	$53.8088	$53.81	$53.80	$53.80
Purchase #2	$33.59	11.867%	$37.5761	$37.58	$37.60	$37.60
Purchase #3	$206.89	7.154%	$221.6909	$221.69	$221.70	$221.70
Purchase #4	$175.80	5.311%	$185.1367	$185.14	$185.15	$185.10
Purchase #5	$203.73	8.550%	$221.1489	$221.15	$221.15	$221.10
Purchase #6	$221.73	7.522%	$238.4085	$238.41	$238.40	$238.40
Purchase #7	$42.30	5.808%	$44.7568	$44.76	$44.75	$44.80
7 purchase totals =	$935.97		$1,002.5267	$1,002.54	$1,002.55	$1,002.50