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	$97.80	11.151%	$108.7057	$108.71	$108.70	$108.70
Purchase #2	$165.25	9.738%	$181.342	$181.34	$181.35	$181.30
Purchase #3	$250.66	11.560%	$279.6363	$279.64	$279.65	$279.60
Purchase #4	$133.74	5.226%	$140.7293	$140.73	$140.75	$140.70
Purchase #5	$156.91	7.542%	$168.7442	$168.74	$168.75	$168.70
Purchase #6	$89.29	11.751%	$99.7825	$99.78	$99.80	$99.80
Purchase #7	$39.44	3.425%	$40.7908	$40.79	$40.80	$40.80
7 purchase totals =	$933.09		$1,019.7308	$1,019.73	$1,019.80	$1,019.60