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	$146.37	3.241%	$151.1139	$151.11	$151.10	$151.10
Purchase #2	$71.91	10.557%	$79.5015	$79.50	$79.50	$79.50
Purchase #3	$167.74	8.507%	$182.0096	$182.01	$182.00	$182.00
Purchase #4	$80.99	11.726%	$90.4869	$90.49	$90.50	$90.50
Purchase #5	$164.36	7.630%	$176.9007	$176.90	$176.90	$176.90
Purchase #6	$61.89	9.450%	$67.7386	$67.74	$67.75	$67.70
Purchase #7	$36.70	3.170%	$37.8634	$37.86	$37.85	$37.90
7 purchase totals =	$729.96		$785.6146	$785.61	$785.60	$785.60