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	$97.97	5.774%	$103.6268	$103.63	$103.65	$103.60
Purchase #2	$105.49	5.502%	$111.2941	$111.29	$111.30	$111.30
Purchase #3	$37.83	11.553%	$42.2005	$42.20	$42.20	$42.20
Purchase #4	$108.33	8.303%	$117.3246	$117.32	$117.30	$117.30
Purchase #5	$6.68	9.554%	$7.3182	$7.32	$7.30	$7.30
Purchase #6	$88.39	4.835%	$92.6637	$92.66	$92.65	$92.70
Purchase #7	$186.31	13.734%	$211.8978	$211.90	$211.90	$211.90
7 purchase totals =	$631.00		$686.3257	$686.32	$686.30	$686.30