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	$199.55	3.663%	$206.8595	$206.86	$206.85	$206.90
Purchase #2	$250.25	5.650%	$264.3891	$264.39	$264.40	$264.40
Purchase #3	$48.43	12.219%	$54.3477	$54.35	$54.35	$54.30
Purchase #4	$17.32	11.802%	$19.3641	$19.36	$19.35	$19.40
Purchase #5	$172.62	13.700%	$196.2689	$196.27	$196.25	$196.30
Purchase #6	$108.66	11.116%	$120.7386	$120.74	$120.75	$120.70
Purchase #7	$189.80	10.410%	$209.5582	$209.56	$209.55	$209.60
7 purchase totals =	$986.63		$1,071.5261	$1,071.53	$1,071.50	$1,071.60