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	$201.34	11.111%	$223.7109	$223.71	$223.70	$223.70
Purchase #2	$92.73	7.370%	$99.5642	$99.56	$99.55	$99.60
Purchase #3	$25.91	13.112%	$29.3073	$29.31	$29.30	$29.30
Purchase #4	$217.81	4.541%	$227.7008	$227.70	$227.70	$227.70
Purchase #5	$210.74	12.169%	$236.385	$236.39	$236.40	$236.40
Purchase #6	$79.78	3.613%	$82.6625	$82.66	$82.65	$82.70
Purchase #7	$77.73	6.620%	$82.8757	$82.88	$82.90	$82.90
7 purchase totals =	$906.04		$982.2064	$982.21	$982.20	$982.30