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	$205.58	3.583%	$212.9459	$212.95	$212.95	$212.90
Purchase #2	$103.87	6.627%	$110.7535	$110.75	$110.75	$110.80
Purchase #3	$106.83	12.624%	$120.3162	$120.32	$120.30	$120.30
Purchase #4	$67.80	5.612%	$71.6049	$71.60	$71.60	$71.60
Purchase #5	$120.89	11.297%	$134.5469	$134.55	$134.55	$134.50
Purchase #6	$240.50	6.219%	$255.4567	$255.46	$255.45	$255.50
Purchase #7	$200.99	10.573%	$222.2407	$222.24	$222.25	$222.20
7 purchase totals =	$1,046.46		$1,127.8648	$1,127.87	$1,127.85	$1,127.80