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	$231.27	5.388%	$243.7308	$243.73	$243.75	$243.70
Purchase #2	$139.45	11.838%	$155.9581	$155.96	$155.95	$156.00
Purchase #3	$82.63	11.249%	$91.925	$91.93	$91.95	$91.90
Purchase #4	$158.31	5.812%	$167.511	$167.51	$167.50	$167.50
Purchase #5	$18.57	5.871%	$19.6602	$19.66	$19.65	$19.70
Purchase #6	$248.98	11.165%	$276.7786	$276.78	$276.80	$276.80
Purchase #7	$81.85	8.817%	$89.0667	$89.07	$89.05	$89.10
7 purchase totals =	$961.06		$1,044.6304	$1,044.64	$1,044.65	$1,044.70