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	$180.58	7.184%	$193.5529	$193.55	$193.55	$193.60
Purchase #2	$102.42	5.656%	$108.2129	$108.21	$108.20	$108.20
Purchase #3	$28.70	12.644%	$32.3288	$32.33	$32.35	$32.30
Purchase #4	$198.94	12.525%	$223.8572	$223.86	$223.85	$223.90
Purchase #5	$167.91	10.686%	$185.8529	$185.85	$185.85	$185.90
Purchase #6	$213.82	7.798%	$230.4937	$230.49	$230.50	$230.50
Purchase #7	$42.71	5.780%	$45.1786	$45.18	$45.20	$45.20
7 purchase totals =	$935.08		$1,019.4770	$1,019.47	$1,019.50	$1,019.60