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	$84.88	3.791%	$88.0978	$88.10	$88.10	$88.10
Purchase #2	$68.31	6.838%	$72.981	$72.98	$73.00	$73.00
Purchase #3	$166.65	11.310%	$185.4981	$185.50	$185.50	$185.50
Purchase #4	$229.67	8.442%	$249.0587	$249.06	$249.05	$249.10
Purchase #5	$59.25	6.824%	$63.2932	$63.29	$63.30	$63.30
Purchase #6	$67.52	6.496%	$71.9061	$71.91	$71.90	$71.90
Purchase #7	$149.88	7.833%	$161.6201	$161.62	$161.60	$161.60
7 purchase totals =	$826.16		$892.4550	$892.46	$892.45	$892.50