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	$183.53	3.485%	$189.926	$189.93	$189.95	$189.90
Purchase #2	$223.58	8.836%	$243.3355	$243.34	$243.35	$243.30
Purchase #3	$114.29	11.744%	$127.7122	$127.71	$127.70	$127.70
Purchase #4	$99.78	12.398%	$112.1507	$112.15	$112.15	$112.20
Purchase #5	$19.51	10.651%	$21.588	$21.59	$21.60	$21.60
Purchase #6	$115.58	9.424%	$126.4723	$126.47	$126.45	$126.50
Purchase #7	$192.32	3.198%	$198.4704	$198.47	$198.45	$198.50
7 purchase totals =	$948.59		$1,019.6551	$1,019.66	$1,019.65	$1,019.70