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	$72.33	4.674%	$75.7107	$75.71	$75.70	$75.70
Purchase #2	$162.92	8.366%	$176.5499	$176.55	$176.55	$176.50
Purchase #3	$65.86	5.456%	$69.4533	$69.45	$69.45	$69.50
Purchase #4	$95.75	3.538%	$99.1376	$99.14	$99.15	$99.10
Purchase #5	$186.46	6.804%	$199.1467	$199.15	$199.15	$199.10
Purchase #6	$82.64	4.637%	$86.472	$86.47	$86.45	$86.50
Purchase #7	$73.95	4.758%	$77.4685	$77.47	$77.45	$77.50
7 purchase totals =	$739.91		$783.9387	$783.94	$783.90	$783.90