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	$191.63	12.397%	$215.3864	$215.39	$215.40	$215.40
Purchase #2	$83.85	7.486%	$90.127	$90.13	$90.15	$90.10
Purchase #3	$99.67	8.480%	$108.122	$108.12	$108.10	$108.10
Purchase #4	$239.98	10.398%	$264.9331	$264.93	$264.95	$264.90
Purchase #5	$68.69	12.803%	$77.4844	$77.48	$77.50	$77.50
Purchase #6	$84.99	5.843%	$89.956	$89.96	$89.95	$90.00
Purchase #7	$168.89	12.259%	$189.5942	$189.59	$189.60	$189.60
7 purchase totals =	$937.70		$1,035.6031	$1,035.60	$1,035.65	$1,035.60