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	$182.50	7.770%	$196.6803	$196.68	$196.70	$196.70
Purchase #2	$50.65	10.275%	$55.8543	$55.85	$55.85	$55.90
Purchase #3	$90.98	9.113%	$99.271	$99.27	$99.25	$99.30
Purchase #4	$227.66	11.483%	$253.8022	$253.80	$253.80	$253.80
Purchase #5	$136.95	13.247%	$155.0918	$155.09	$155.10	$155.10
Purchase #6	$48.76	4.872%	$51.1356	$51.14	$51.15	$51.10
Purchase #7	$32.28	12.536%	$36.3266	$36.33	$36.35	$36.30
7 purchase totals =	$769.78		$848.1618	$848.16	$848.20	$848.20