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	$193.80	4.488%	$202.4977	$202.50	$202.50	$202.50
Purchase #2	$22.48	11.515%	$25.0686	$25.07	$25.05	$25.10
Purchase #3	$111.80	7.471%	$120.1526	$120.15	$120.15	$120.20
Purchase #4	$145.88	11.607%	$162.8123	$162.81	$162.80	$162.80
Purchase #5	$198.34	12.692%	$223.5133	$223.51	$223.50	$223.50
Purchase #6	$58.62	12.488%	$65.9405	$65.94	$65.95	$65.90
Purchase #7	$206.58	4.721%	$216.3326	$216.33	$216.35	$216.30
7 purchase totals =	$937.50		$1,016.3176	$1,016.31	$1,016.30	$1,016.30