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	$161.71	5.393%	$170.431	$170.43	$170.45	$170.40
Purchase #2	$38.69	9.831%	$42.4936	$42.49	$42.50	$42.50
Purchase #3	$188.82	6.352%	$200.8138	$200.81	$200.80	$200.80
Purchase #4	$17.87	13.195%	$20.2279	$20.23	$20.25	$20.20
Purchase #5	$177.95	12.688%	$200.5283	$200.53	$200.55	$200.50
Purchase #6	$161.33	7.206%	$172.9554	$172.96	$172.95	$173.00
Purchase #7	$231.46	5.251%	$243.614	$243.61	$243.60	$243.60
7 purchase totals =	$977.83		$1,051.0640	$1,051.06	$1,051.10	$1,051.00