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	$66.38	7.163%	$71.1348	$71.13	$71.15	$71.10
Purchase #2	$161.64	10.808%	$179.1101	$179.11	$179.10	$179.10
Purchase #3	$187.31	11.624%	$209.0829	$209.08	$209.10	$209.10
Purchase #4	$177.86	9.387%	$194.5557	$194.56	$194.55	$194.60
Purchase #5	$159.60	5.597%	$168.5328	$168.53	$168.55	$168.50
Purchase #6	$243.66	6.144%	$258.6305	$258.63	$258.65	$258.60
Purchase #7	$77.83	10.321%	$85.8628	$85.86	$85.85	$85.90
7 purchase totals =	$1,074.28		$1,166.9096	$1,166.90	$1,166.95	$1,166.90