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	$174.57	6.508%	$185.931	$185.93	$185.95	$185.90
Purchase #2	$129.59	10.847%	$143.6466	$143.65	$143.65	$143.60
Purchase #3	$91.54	9.283%	$100.0377	$100.04	$100.05	$100.00
Purchase #4	$167.45	9.530%	$183.408	$183.41	$183.40	$183.40
Purchase #5	$73.40	12.399%	$82.5009	$82.50	$82.50	$82.50
Purchase #6	$246.45	11.871%	$275.7061	$275.71	$275.70	$275.70
Purchase #7	$141.67	6.141%	$150.37	$150.37	$150.35	$150.40
7 purchase totals =	$1,024.67		$1,121.6003	$1,121.61	$1,121.60	$1,121.50