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	$207.56	7.654%	$223.4466	$223.45	$223.45	$223.40
Purchase #2	$104.46	6.463%	$111.2112	$111.21	$111.20	$111.20
Purchase #3	$114.82	10.190%	$126.5202	$126.52	$126.50	$126.50
Purchase #4	$106.88	4.763%	$111.9707	$111.97	$111.95	$112.00
Purchase #5	$183.51	5.237%	$193.1204	$193.12	$193.10	$193.10
Purchase #6	$148.72	8.653%	$161.5887	$161.59	$161.60	$161.60
Purchase #7	$234.88	4.716%	$245.9569	$245.96	$245.95	$246.00
7 purchase totals =	$1,100.83		$1,173.8147	$1,173.82	$1,173.75	$1,173.80