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	$250.56	10.115%	$275.9041	$275.90	$275.90	$275.90
Purchase #2	$93.25	13.290%	$105.6429	$105.64	$105.65	$105.60
Purchase #3	$104.77	3.615%	$108.5574	$108.56	$108.55	$108.60
Purchase #4	$38.29	10.678%	$42.3786	$42.38	$42.40	$42.40
Purchase #5	$238.89	11.332%	$265.961	$265.96	$265.95	$266.00
Purchase #6	$152.74	3.704%	$158.3975	$158.40	$158.40	$158.40
Purchase #7	$195.76	7.858%	$211.1428	$211.14	$211.15	$211.10
7 purchase totals =	$1,074.26		$1,167.9843	$1,167.98	$1,168.00	$1,168.00