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	$207.57	7.360%	$222.8472	$222.85	$222.85	$222.80
Purchase #2	$42.26	10.599%	$46.7391	$46.74	$46.75	$46.70
Purchase #3	$48.56	12.557%	$54.6577	$54.66	$54.65	$54.70
Purchase #4	$136.32	13.603%	$154.8636	$154.86	$154.85	$154.90
Purchase #5	$92.53	12.806%	$104.3794	$104.38	$104.40	$104.40
Purchase #6	$127.75	10.841%	$141.5994	$141.60	$141.60	$141.60
Purchase #7	$201.95	10.414%	$222.9811	$222.98	$223.00	$223.00
7 purchase totals =	$856.94		$948.0675	$948.07	$948.10	$948.10