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	$250.60	5.197%	$263.6237	$263.62	$263.60	$263.60
Purchase #2	$213.51	4.560%	$223.2461	$223.25	$223.25	$223.20
Purchase #3	$156.63	10.465%	$173.0213	$173.02	$173.00	$173.00
Purchase #4	$33.66	11.299%	$37.4632	$37.46	$37.45	$37.50
Purchase #5	$141.97	12.398%	$159.5714	$159.57	$159.55	$159.60
Purchase #6	$121.88	6.754%	$130.1118	$130.11	$130.10	$130.10
Purchase #7	$63.79	12.628%	$71.8454	$71.85	$71.85	$71.80
7 purchase totals =	$982.04		$1,058.8829	$1,058.88	$1,058.80	$1,058.80