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	$135.63	8.533%	$147.2033	$147.20	$147.20	$147.20
Purchase #2	$90.88	11.627%	$101.4466	$101.45	$101.45	$101.40
Purchase #3	$103.37	5.219%	$108.7649	$108.76	$108.75	$108.80
Purchase #4	$131.55	10.141%	$144.8905	$144.89	$144.90	$144.90
Purchase #5	$93.83	11.531%	$104.6495	$104.65	$104.65	$104.60
Purchase #6	$193.71	11.638%	$216.254	$216.25	$216.25	$216.30
Purchase #7	$237.46	7.414%	$255.0653	$255.07	$255.05	$255.10
7 purchase totals =	$986.43		$1,078.2741	$1,078.27	$1,078.25	$1,078.30