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	$164.52	10.281%	$181.4343	$181.43	$181.45	$181.40
Purchase #2	$99.36	10.329%	$109.6229	$109.62	$109.60	$109.60
Purchase #3	$161.47	5.537%	$170.4106	$170.41	$170.40	$170.40
Purchase #4	$34.46	11.841%	$38.5404	$38.54	$38.55	$38.50
Purchase #5	$238.31	9.282%	$260.4299	$260.43	$260.45	$260.40
Purchase #6	$71.53	12.863%	$80.7309	$80.73	$80.75	$80.70
Purchase #7	$160.49	11.687%	$179.2465	$179.25	$179.25	$179.20
7 purchase totals =	$930.14		$1,020.4155	$1,020.41	$1,020.45	$1,020.20