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	$150.60	3.199%	$155.4177	$155.42	$155.40	$155.40
Purchase #2	$145.32	9.600%	$159.2707	$159.27	$159.25	$159.30
Purchase #3	$54.79	4.513%	$57.2627	$57.26	$57.25	$57.30
Purchase #4	$55.64	12.608%	$62.6551	$62.66	$62.65	$62.70
Purchase #5	$174.88	9.127%	$190.8413	$190.84	$190.85	$190.80
Purchase #6	$193.37	3.255%	$199.6642	$199.66	$199.65	$199.70
Purchase #7	$119.30	4.146%	$124.2462	$124.25	$124.25	$124.20
7 purchase totals =	$893.90		$949.3579	$949.36	$949.30	$949.40