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	$156.55	3.268%	$161.6661	$161.67	$161.65	$161.70
Purchase #2	$89.45	13.766%	$101.7637	$101.76	$101.75	$101.80
Purchase #3	$46.33	9.343%	$50.6586	$50.66	$50.65	$50.70
Purchase #4	$98.41	5.215%	$103.5421	$103.54	$103.55	$103.50
Purchase #5	$163.42	7.632%	$175.8922	$175.89	$175.90	$175.90
Purchase #6	$221.95	8.414%	$240.6249	$240.62	$240.60	$240.60
Purchase #7	$249.50	10.232%	$275.0288	$275.03	$275.05	$275.00
7 purchase totals =	$1,025.61		$1,109.1764	$1,109.17	$1,109.15	$1,109.20