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	$116.59	12.346%	$130.9842	$130.98	$131.00	$131.00
Purchase #2	$117.68	10.637%	$130.1976	$130.20	$130.20	$130.20
Purchase #3	$195.71	9.555%	$214.4101	$214.41	$214.40	$214.40
Purchase #4	$179.88	8.166%	$194.569	$194.57	$194.55	$194.60
Purchase #5	$249.33	5.849%	$263.9133	$263.91	$263.90	$263.90
Purchase #6	$113.45	4.730%	$118.8162	$118.82	$118.80	$118.80
Purchase #7	$88.32	13.855%	$100.5567	$100.56	$100.55	$100.60
7 purchase totals =	$1,060.96		$1,153.4471	$1,153.45	$1,153.40	$1,153.50