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	$101.68	3.425%	$105.1625	$105.16	$105.15	$105.20
Purchase #2	$38.91	13.835%	$44.2932	$44.29	$44.30	$44.30
Purchase #3	$112.66	12.801%	$127.0816	$127.08	$127.10	$127.10
Purchase #4	$68.70	4.578%	$71.8451	$71.85	$71.85	$71.80
Purchase #5	$223.34	12.645%	$251.5813	$251.58	$251.60	$251.60
Purchase #6	$99.35	5.192%	$104.5083	$104.51	$104.50	$104.50
Purchase #7	$38.74	13.777%	$44.0772	$44.08	$44.10	$44.10
7 purchase totals =	$683.38		$748.5492	$748.55	$748.60	$748.60