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	$179.27	4.178%	$186.7599	$186.76	$186.75	$186.80
Purchase #2	$150.26	4.403%	$156.8759	$156.88	$156.90	$156.90
Purchase #3	$247.54	5.261%	$260.5631	$260.56	$260.55	$260.60
Purchase #4	$189.92	7.547%	$204.2533	$204.25	$204.25	$204.30
Purchase #5	$174.65	11.693%	$195.0718	$195.07	$195.05	$195.10
Purchase #6	$170.53	11.681%	$190.4496	$190.45	$190.45	$190.40
Purchase #7	$113.94	11.827%	$127.4157	$127.42	$127.40	$127.40
7 purchase totals =	$1,226.11		$1,321.3893	$1,321.39	$1,321.35	$1,321.50