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	$235.77	5.375%	$248.4426	$248.44	$248.45	$248.40
Purchase #2	$78.42	4.376%	$81.8517	$81.85	$81.85	$81.90
Purchase #3	$123.55	11.842%	$138.1808	$138.18	$138.20	$138.20
Purchase #4	$210.71	8.323%	$228.2474	$228.25	$228.25	$228.20
Purchase #5	$94.91	11.530%	$105.8531	$105.85	$105.85	$105.90
Purchase #6	$250.41	6.162%	$265.8403	$265.84	$265.85	$265.80
Purchase #7	$30.69	5.797%	$32.4691	$32.47	$32.45	$32.50
7 purchase totals =	$1,024.46		$1,100.8850	$1,100.88	$1,100.90	$1,100.90