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	$128.83	10.573%	$142.4512	$142.45	$142.45	$142.50
Purchase #2	$28.88	8.230%	$31.2568	$31.26	$31.25	$31.30
Purchase #3	$167.88	13.260%	$190.1409	$190.14	$190.15	$190.10
Purchase #4	$179.60	5.186%	$188.9141	$188.91	$188.90	$188.90
Purchase #5	$192.58	11.837%	$215.3757	$215.38	$215.40	$215.40
Purchase #6	$129.49	5.281%	$136.3284	$136.33	$136.35	$136.30
Purchase #7	$69.69	3.720%	$72.2825	$72.28	$72.30	$72.30
7 purchase totals =	$896.95		$976.7496	$976.75	$976.80	$976.80