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	$93.28	13.156%	$105.5519	$105.55	$105.55	$105.60
Purchase #2	$19.63	6.372%	$20.8808	$20.88	$20.90	$20.90
Purchase #3	$44.73	9.794%	$49.1109	$49.11	$49.10	$49.10
Purchase #4	$210.45	5.407%	$221.829	$221.83	$221.85	$221.80
Purchase #5	$185.52	8.143%	$200.6269	$200.63	$200.65	$200.60
Purchase #6	$49.48	11.252%	$55.0475	$55.05	$55.05	$55.00
Purchase #7	$189.39	10.765%	$209.7778	$209.78	$209.80	$209.80
7 purchase totals =	$792.48		$862.8248	$862.83	$862.90	$862.80