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	$212.85	11.461%	$237.2447	$237.24	$237.25	$237.20
Purchase #2	$152.75	5.237%	$160.7495	$160.75	$160.75	$160.70
Purchase #3	$156.32	7.780%	$168.4817	$168.48	$168.50	$168.50
Purchase #4	$38.36	7.513%	$41.242	$41.24	$41.25	$41.20
Purchase #5	$243.38	6.199%	$258.4671	$258.47	$258.45	$258.50
Purchase #6	$65.85	8.846%	$71.6751	$71.68	$71.70	$71.70
Purchase #7	$89.59	11.422%	$99.823	$99.82	$99.80	$99.80
7 purchase totals =	$959.10		$1,037.6831	$1,037.68	$1,037.70	$1,037.60