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	$28.97	13.364%	$32.8416	$32.84	$32.85	$32.80
Purchase #2	$55.59	12.137%	$62.337	$62.34	$62.35	$62.30
Purchase #3	$217.42	12.671%	$244.9693	$244.97	$244.95	$245.00
Purchase #4	$149.40	4.479%	$156.0916	$156.09	$156.10	$156.10
Purchase #5	$58.94	5.359%	$62.0986	$62.10	$62.10	$62.10
Purchase #6	$64.35	12.861%	$72.6261	$72.63	$72.65	$72.60
Purchase #7	$135.72	11.651%	$151.5327	$151.53	$151.55	$151.50
7 purchase totals =	$710.39		$782.4969	$782.50	$782.55	$782.40