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	$199.60	8.417%	$216.4003	$216.40	$216.40	$216.40
Purchase #2	$116.31	3.299%	$120.1471	$120.15	$120.15	$120.10
Purchase #3	$147.85	3.415%	$152.8991	$152.90	$152.90	$152.90
Purchase #4	$124.29	9.843%	$136.5239	$136.52	$136.50	$136.50
Purchase #5	$5.34	6.198%	$5.671	$5.67	$5.65	$5.70
Purchase #6	$233.83	11.873%	$261.5926	$261.59	$261.60	$261.60
Purchase #7	$99.37	10.215%	$109.5206	$109.52	$109.50	$109.50
7 purchase totals =	$926.59		$1,002.7546	$1,002.75	$1,002.70	$1,002.70