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	$126.78	12.663%	$142.8342	$142.83	$142.85	$142.80
Purchase #2	$192.56	9.626%	$211.0958	$211.10	$211.10	$211.10
Purchase #3	$226.52	13.851%	$257.8953	$257.90	$257.90	$257.90
Purchase #4	$113.76	11.656%	$127.0199	$127.02	$127.00	$127.00
Purchase #5	$224.47	11.666%	$250.6567	$250.66	$250.65	$250.70
Purchase #6	$186.27	7.137%	$199.5641	$199.56	$199.55	$199.60
Purchase #7	$241.80	4.170%	$251.8831	$251.88	$251.90	$251.90
7 purchase totals =	$1,312.16		$1,440.9491	$1,440.95	$1,440.95	$1,441.00