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	$178.32	7.119%	$191.0146	$191.01	$191.00	$191.00
Purchase #2	$235.89	3.610%	$244.4056	$244.41	$244.40	$244.40
Purchase #3	$44.47	7.718%	$47.9022	$47.90	$47.90	$47.90
Purchase #4	$215.78	7.200%	$231.3162	$231.32	$231.30	$231.30
Purchase #5	$43.40	4.491%	$45.3491	$45.35	$45.35	$45.30
Purchase #6	$140.92	5.642%	$148.8707	$148.87	$148.85	$148.90
Purchase #7	$166.79	5.601%	$176.1319	$176.13	$176.15	$176.10
7 purchase totals =	$1,025.57		$1,084.9903	$1,084.99	$1,084.95	$1,084.90