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	$32.39	11.523%	$36.1223	$36.12	$36.10	$36.10
Purchase #2	$231.93	8.158%	$250.8508	$250.85	$250.85	$250.90
Purchase #3	$195.94	9.450%	$214.4563	$214.46	$214.45	$214.50
Purchase #4	$183.73	13.760%	$209.0112	$209.01	$209.00	$209.00
Purchase #5	$111.60	6.293%	$118.623	$118.62	$118.60	$118.60
Purchase #6	$54.69	8.828%	$59.518	$59.52	$59.50	$59.50
Purchase #7	$160.90	8.827%	$175.1026	$175.10	$175.10	$175.10
7 purchase totals =	$971.18		$1,063.6842	$1,063.68	$1,063.60	$1,063.70