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	$190.34	6.771%	$203.2279	$203.23	$203.25	$203.20
Purchase #2	$32.90	13.290%	$37.2724	$37.27	$37.25	$37.30
Purchase #3	$6.80	9.423%	$7.4408	$7.44	$7.45	$7.40
Purchase #4	$160.79	10.795%	$178.1473	$178.15	$178.15	$178.10
Purchase #5	$131.58	5.271%	$138.5156	$138.52	$138.50	$138.50
Purchase #6	$200.71	9.541%	$219.8597	$219.86	$219.85	$219.90
Purchase #7	$58.52	6.680%	$62.4291	$62.43	$62.45	$62.40
7 purchase totals =	$781.64		$846.8928	$846.90	$846.90	$846.80