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	$199.92	11.869%	$223.6485	$223.65	$223.65	$223.60
Purchase #2	$92.28	8.712%	$100.3194	$100.32	$100.30	$100.30
Purchase #3	$6.59	11.279%	$7.3333	$7.33	$7.35	$7.30
Purchase #4	$87.35	10.547%	$96.5628	$96.56	$96.55	$96.60
Purchase #5	$181.66	12.223%	$203.8643	$203.86	$203.85	$203.90
Purchase #6	$189.64	8.500%	$205.7594	$205.76	$205.75	$205.80
Purchase #7	$122.32	5.311%	$128.8164	$128.82	$128.80	$128.80
7 purchase totals =	$879.76		$966.3041	$966.30	$966.25	$966.30