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	$62.42	4.725%	$65.3693	$65.37	$65.35	$65.40
Purchase #2	$56.49	10.234%	$62.2712	$62.27	$62.25	$62.30
Purchase #3	$184.66	6.484%	$196.6334	$196.63	$196.65	$196.60
Purchase #4	$48.57	10.138%	$53.494	$53.49	$53.50	$53.50
Purchase #5	$187.39	13.443%	$212.5808	$212.58	$212.60	$212.60
Purchase #6	$47.84	5.162%	$50.3095	$50.31	$50.30	$50.30
Purchase #7	$146.36	7.368%	$157.1438	$157.14	$157.15	$157.10
7 purchase totals =	$733.73		$797.8020	$797.79	$797.80	$797.80