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	$72.90	7.144%	$78.108	$78.11	$78.10	$78.10
Purchase #2	$21.81	4.797%	$22.8562	$22.86	$22.85	$22.90
Purchase #3	$43.64	9.346%	$47.7186	$47.72	$47.70	$47.70
Purchase #4	$78.47	9.258%	$85.7348	$85.73	$85.75	$85.70
Purchase #5	$167.58	12.504%	$188.5342	$188.53	$188.55	$188.50
Purchase #6	$95.68	4.566%	$100.0487	$100.05	$100.05	$100.00
Purchase #7	$250.93	5.230%	$264.0536	$264.05	$264.05	$264.10
7 purchase totals =	$731.01		$787.0541	$787.05	$787.05	$787.00