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	$174.79	8.721%	$190.0334	$190.03	$190.05	$190.00
Purchase #2	$238.71	12.613%	$268.8185	$268.82	$268.80	$268.80
Purchase #3	$58.66	12.771%	$66.1515	$66.15	$66.15	$66.20
Purchase #4	$145.58	4.610%	$152.2912	$152.29	$152.30	$152.30
Purchase #5	$218.55	7.684%	$235.3434	$235.34	$235.35	$235.30
Purchase #6	$53.54	6.862%	$57.2139	$57.21	$57.20	$57.20
Purchase #7	$75.48	13.365%	$85.5679	$85.57	$85.55	$85.60
7 purchase totals =	$965.31		$1,055.4198	$1,055.41	$1,055.40	$1,055.40