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	$223.50	6.591%	$238.2309	$238.23	$238.25	$238.20
Purchase #2	$28.82	11.856%	$32.2369	$32.24	$32.25	$32.20
Purchase #3	$165.48	12.177%	$185.6305	$185.63	$185.65	$185.60
Purchase #4	$137.54	6.532%	$146.5241	$146.52	$146.50	$146.50
Purchase #5	$231.53	3.129%	$238.7746	$238.77	$238.75	$238.80
Purchase #6	$24.83	4.581%	$25.9675	$25.97	$25.95	$26.00
Purchase #7	$240.76	8.632%	$261.5424	$261.54	$261.55	$261.50
7 purchase totals =	$1,052.46		$1,128.9069	$1,128.90	$1,128.90	$1,128.80