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	$172.57	4.276%	$179.9491	$179.95	$179.95	$179.90
Purchase #2	$236.29	8.212%	$255.6941	$255.69	$255.70	$255.70
Purchase #3	$28.34	9.845%	$31.1301	$31.13	$31.15	$31.10
Purchase #4	$196.92	9.726%	$216.0724	$216.07	$216.05	$216.10
Purchase #5	$178.65	11.126%	$198.5266	$198.53	$198.55	$198.50
Purchase #6	$175.53	4.164%	$182.8391	$182.84	$182.85	$182.80
Purchase #7	$103.52	4.633%	$108.3161	$108.32	$108.30	$108.30
7 purchase totals =	$1,091.82		$1,172.5275	$1,172.53	$1,172.55	$1,172.40