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	$125.92	3.354%	$130.1434	$130.14	$130.15	$130.10
Purchase #2	$207.39	12.517%	$233.349	$233.35	$233.35	$233.30
Purchase #3	$219.46	4.611%	$229.5793	$229.58	$229.60	$229.60
Purchase #4	$216.82	3.837%	$225.1394	$225.14	$225.15	$225.10
Purchase #5	$59.32	13.818%	$67.5168	$67.52	$67.50	$67.50
Purchase #6	$194.66	7.660%	$209.571	$209.57	$209.55	$209.60
Purchase #7	$37.56	12.180%	$42.1348	$42.13	$42.15	$42.10
7 purchase totals =	$1,061.13		$1,137.4337	$1,137.43	$1,137.45	$1,137.30