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	$130.53	4.139%	$135.9326	$135.93	$135.95	$135.90
Purchase #2	$127.86	10.693%	$141.5321	$141.53	$141.55	$141.50
Purchase #3	$69.53	12.777%	$78.4138	$78.41	$78.40	$78.40
Purchase #4	$180.47	6.809%	$192.7582	$192.76	$192.75	$192.80
Purchase #5	$130.56	11.854%	$146.0366	$146.04	$146.05	$146.00
Purchase #6	$95.60	9.194%	$104.3895	$104.39	$104.40	$104.40
Purchase #7	$204.56	8.438%	$221.8208	$221.82	$221.80	$221.80
7 purchase totals =	$939.11		$1,020.8836	$1,020.88	$1,020.90	$1,020.80