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	$23.90	3.263%	$24.6799	$24.68	$24.70	$24.70
Purchase #2	$93.42	6.560%	$99.5484	$99.55	$99.55	$99.50
Purchase #3	$245.51	4.506%	$256.5727	$256.57	$256.55	$256.60
Purchase #4	$85.56	4.475%	$89.3888	$89.39	$89.40	$89.40
Purchase #5	$182.34	5.607%	$192.5638	$192.56	$192.55	$192.60
Purchase #6	$34.27	3.380%	$35.4283	$35.43	$35.45	$35.40
Purchase #7	$211.85	9.817%	$232.6473	$232.65	$232.65	$232.60
7 purchase totals =	$876.85		$930.8292	$930.83	$930.85	$930.80