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	$148.42	8.179%	$160.5593	$160.56	$160.55	$160.60
Purchase #2	$108.33	11.244%	$120.5106	$120.51	$120.50	$120.50
Purchase #3	$50.96	6.411%	$54.227	$54.23	$54.25	$54.20
Purchase #4	$67.49	5.850%	$71.4382	$71.44	$71.45	$71.40
Purchase #5	$70.67	11.193%	$78.5801	$78.58	$78.60	$78.60
Purchase #6	$17.99	7.424%	$19.3256	$19.33	$19.35	$19.30
Purchase #7	$209.54	11.722%	$234.1023	$234.10	$234.10	$234.10
7 purchase totals =	$673.40		$738.7431	$738.75	$738.80	$738.70