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	$81.62	6.131%	$86.6241	$86.62	$86.60	$86.60
Purchase #2	$79.29	4.427%	$82.8002	$82.80	$82.80	$82.80
Purchase #3	$110.85	11.482%	$123.5778	$123.58	$123.60	$123.60
Purchase #4	$222.25	11.438%	$247.671	$247.67	$247.65	$247.70
Purchase #5	$198.81	4.569%	$207.8936	$207.89	$207.90	$207.90
Purchase #6	$113.26	10.658%	$125.3313	$125.33	$125.35	$125.30
Purchase #7	$200.93	5.567%	$212.1158	$212.12	$212.10	$212.10
7 purchase totals =	$1,007.01		$1,086.0138	$1,086.01	$1,086.00	$1,086.00