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	$133.55	6.867%	$142.7209	$142.72	$142.70	$142.70
Purchase #2	$108.97	11.396%	$121.3882	$121.39	$121.40	$121.40
Purchase #3	$30.49	8.286%	$33.0164	$33.02	$33.00	$33.00
Purchase #4	$200.76	4.651%	$210.0973	$210.10	$210.10	$210.10
Purchase #5	$57.83	6.457%	$61.5641	$61.56	$61.55	$61.60
Purchase #6	$141.75	7.531%	$152.4252	$152.43	$152.45	$152.40
Purchase #7	$73.85	6.127%	$78.3748	$78.37	$78.35	$78.40
7 purchase totals =	$747.20		$799.5869	$799.59	$799.55	$799.60