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	$202.57	5.376%	$213.4602	$213.46	$213.45	$213.50
Purchase #2	$102.70	3.437%	$106.2298	$106.23	$106.25	$106.20
Purchase #3	$236.71	11.464%	$263.8464	$263.85	$263.85	$263.80
Purchase #4	$174.78	5.645%	$184.6463	$184.65	$184.65	$184.60
Purchase #5	$243.32	12.442%	$273.5939	$273.59	$273.60	$273.60
Purchase #6	$12.85	4.198%	$13.3894	$13.39	$13.40	$13.40
Purchase #7	$37.72	6.732%	$40.2593	$40.26	$40.25	$40.30
7 purchase totals =	$1,010.65		$1,095.4253	$1,095.43	$1,095.45	$1,095.40