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	$102.80	11.747%	$114.8759	$114.88	$114.90	$114.90
Purchase #2	$61.76	11.185%	$68.6679	$68.67	$68.65	$68.70
Purchase #3	$140.37	8.206%	$151.8888	$151.89	$151.90	$151.90
Purchase #4	$162.43	6.103%	$172.3431	$172.34	$172.35	$172.30
Purchase #5	$127.28	10.787%	$141.0097	$141.01	$141.00	$141.00
Purchase #6	$150.86	8.774%	$164.0965	$164.10	$164.10	$164.10
Purchase #7	$141.82	12.628%	$159.729	$159.73	$159.75	$159.70
7 purchase totals =	$887.32		$972.6109	$972.62	$972.65	$972.60