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	$199.42	11.356%	$222.0661	$222.07	$222.05	$222.10
Purchase #2	$90.49	8.690%	$98.3536	$98.35	$98.35	$98.40
Purchase #3	$74.43	5.620%	$78.613	$78.61	$78.60	$78.60
Purchase #4	$35.92	5.299%	$37.8234	$37.82	$37.80	$37.80
Purchase #5	$243.35	11.349%	$270.9678	$270.97	$270.95	$271.00
Purchase #6	$126.96	6.440%	$135.1362	$135.14	$135.15	$135.10
Purchase #7	$99.70	12.136%	$111.7996	$111.80	$111.80	$111.80
7 purchase totals =	$870.27		$954.7597	$954.76	$954.70	$954.80