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	$218.86	8.584%	$237.6469	$237.65	$237.65	$237.60
Purchase #2	$162.46	11.617%	$181.333	$181.33	$181.35	$181.30
Purchase #3	$232.61	9.301%	$254.2451	$254.25	$254.25	$254.20
Purchase #4	$164.61	3.718%	$170.7302	$170.73	$170.75	$170.70
Purchase #5	$33.66	12.579%	$37.8941	$37.89	$37.90	$37.90
Purchase #6	$104.37	5.313%	$109.9152	$109.92	$109.90	$109.90
Purchase #7	$208.95	11.748%	$233.4974	$233.50	$233.50	$233.50
7 purchase totals =	$1,125.52		$1,225.2619	$1,225.27	$1,225.30	$1,225.10