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	$153.81	13.428%	$174.4636	$174.46	$174.45	$174.50
Purchase #2	$89.51	12.345%	$100.56	$100.56	$100.55	$100.60
Purchase #3	$122.83	12.737%	$138.4749	$138.47	$138.45	$138.50
Purchase #4	$64.97	6.751%	$69.3561	$69.36	$69.35	$69.40
Purchase #5	$41.26	12.521%	$46.4262	$46.43	$46.45	$46.40
Purchase #6	$44.37	6.709%	$47.3468	$47.35	$47.35	$47.30
Purchase #7	$204.64	9.341%	$223.7554	$223.76	$223.75	$223.80
7 purchase totals =	$721.39		$800.3830	$800.39	$800.35	$800.50