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	$94.47	12.150%	$105.9481	$105.95	$105.95	$105.90
Purchase #2	$167.67	8.617%	$182.1181	$182.12	$182.10	$182.10
Purchase #3	$62.93	5.454%	$66.3622	$66.36	$66.35	$66.40
Purchase #4	$109.72	13.516%	$124.5498	$124.55	$124.55	$124.50
Purchase #5	$55.43	8.728%	$60.2679	$60.27	$60.25	$60.30
Purchase #6	$188.45	12.633%	$212.2569	$212.26	$212.25	$212.30
Purchase #7	$65.60	10.858%	$72.7228	$72.72	$72.70	$72.70
7 purchase totals =	$744.27		$824.2258	$824.23	$824.15	$824.20