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	$131.73	8.424%	$142.8269	$142.83	$142.85	$142.80
Purchase #2	$203.48	3.631%	$210.8684	$210.87	$210.85	$210.90
Purchase #3	$26.33	5.755%	$27.8453	$27.85	$27.85	$27.80
Purchase #4	$157.69	8.630%	$171.2986	$171.30	$171.30	$171.30
Purchase #5	$221.33	4.319%	$230.8892	$230.89	$230.90	$230.90
Purchase #6	$214.85	4.408%	$224.3206	$224.32	$224.30	$224.30
Purchase #7	$90.57	10.753%	$100.309	$100.31	$100.30	$100.30
7 purchase totals =	$1,045.98		$1,108.3580	$1,108.37	$1,108.35	$1,108.30