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	$69.67	10.715%	$77.1351	$77.14	$77.15	$77.10
Purchase #2	$68.42	12.869%	$77.225	$77.23	$77.25	$77.20
Purchase #3	$191.51	12.559%	$215.5617	$215.56	$215.55	$215.60
Purchase #4	$142.61	6.484%	$151.8568	$151.86	$151.85	$151.90
Purchase #5	$246.79	8.558%	$267.9103	$267.91	$267.90	$267.90
Purchase #6	$187.58	4.735%	$196.4619	$196.46	$196.45	$196.50
Purchase #7	$146.42	10.569%	$161.8951	$161.90	$161.90	$161.90
7 purchase totals =	$1,053.00		$1,148.0459	$1,148.06	$1,148.05	$1,148.10