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	$70.25	3.734%	$72.8731	$72.87	$72.85	$72.90
Purchase #2	$68.61	4.419%	$71.6419	$71.64	$71.65	$71.60
Purchase #3	$127.32	9.426%	$139.3212	$139.32	$139.30	$139.30
Purchase #4	$34.55	5.123%	$36.32	$36.32	$36.30	$36.30
Purchase #5	$208.35	9.754%	$228.6725	$228.67	$228.65	$228.70
Purchase #6	$100.73	9.774%	$110.5754	$110.58	$110.60	$110.60
Purchase #7	$52.38	3.642%	$54.2877	$54.29	$54.30	$54.30
7 purchase totals =	$662.19		$713.6918	$713.69	$713.65	$713.70