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	$140.28	3.442%	$145.1084	$145.11	$145.10	$145.10
Purchase #2	$226.53	10.870%	$251.1538	$251.15	$251.15	$251.20
Purchase #3	$51.65	10.590%	$57.1197	$57.12	$57.10	$57.10
Purchase #4	$157.75	4.681%	$165.1343	$165.13	$165.15	$165.10
Purchase #5	$59.33	3.112%	$61.1763	$61.18	$61.20	$61.20
Purchase #6	$141.44	7.339%	$151.8203	$151.82	$151.80	$151.80
Purchase #7	$130.39	12.813%	$147.0969	$147.10	$147.10	$147.10
7 purchase totals =	$907.37		$978.6097	$978.61	$978.60	$978.60