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	$233.32	8.817%	$253.8918	$253.89	$253.90	$253.90
Purchase #2	$92.62	11.231%	$103.0222	$103.02	$103.00	$103.00
Purchase #3	$239.40	3.711%	$248.2841	$248.28	$248.30	$248.30
Purchase #4	$65.55	10.454%	$72.4026	$72.40	$72.40	$72.40
Purchase #5	$89.49	3.175%	$92.3313	$92.33	$92.35	$92.30
Purchase #6	$85.97	5.716%	$90.884	$90.88	$90.90	$90.90
Purchase #7	$187.51	12.266%	$210.51	$210.51	$210.50	$210.50
7 purchase totals =	$993.86		$1,071.3260	$1,071.31	$1,071.35	$1,071.30