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	$211.59	12.774%	$238.6185	$238.62	$238.60	$238.60
Purchase #2	$218.88	6.841%	$233.8536	$233.85	$233.85	$233.90
Purchase #3	$234.96	6.530%	$250.3029	$250.30	$250.30	$250.30
Purchase #4	$91.55	9.739%	$100.4661	$100.47	$100.45	$100.50
Purchase #5	$71.62	7.241%	$76.806	$76.81	$76.80	$76.80
Purchase #6	$126.26	4.157%	$131.5086	$131.51	$131.50	$131.50
Purchase #7	$167.84	8.576%	$182.234	$182.23	$182.25	$182.20
7 purchase totals =	$1,122.70		$1,213.7897	$1,213.79	$1,213.75	$1,213.80