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	$148.31	10.798%	$164.3245	$164.32	$164.30	$164.30
Purchase #2	$20.81	6.550%	$22.1731	$22.17	$22.15	$22.20
Purchase #3	$69.48	10.764%	$76.9588	$76.96	$76.95	$77.00
Purchase #4	$205.53	11.667%	$229.5092	$229.51	$229.50	$229.50
Purchase #5	$229.26	9.315%	$250.6156	$250.62	$250.60	$250.60
Purchase #6	$179.46	11.573%	$200.2289	$200.23	$200.25	$200.20
Purchase #7	$13.82	5.537%	$14.5852	$14.59	$14.60	$14.60
7 purchase totals =	$866.67		$958.3953	$958.40	$958.35	$958.40