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	$90.30	10.150%	$99.4655	$99.47	$99.45	$99.50
Purchase #2	$94.76	11.823%	$105.9635	$105.96	$105.95	$106.00
Purchase #3	$191.47	4.815%	$200.6893	$200.69	$200.70	$200.70
Purchase #4	$112.73	3.370%	$116.529	$116.53	$116.55	$116.50
Purchase #5	$140.71	4.651%	$147.2544	$147.25	$147.25	$147.30
Purchase #6	$167.37	13.326%	$189.6737	$189.67	$189.65	$189.70
Purchase #7	$65.39	5.347%	$68.8864	$68.89	$68.90	$68.90
7 purchase totals =	$862.73		$928.4618	$928.46	$928.45	$928.60