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	$175.82	5.462%	$185.4233	$185.42	$185.40	$185.40
Purchase #2	$60.25	7.615%	$64.838	$64.84	$64.85	$64.80
Purchase #3	$208.65	6.346%	$221.8909	$221.89	$221.90	$221.90
Purchase #4	$60.57	11.370%	$67.4568	$67.46	$67.45	$67.50
Purchase #5	$248.99	13.113%	$281.6401	$281.64	$281.65	$281.60
Purchase #6	$107.98	6.713%	$115.2287	$115.23	$115.25	$115.20
Purchase #7	$108.56	11.307%	$120.8349	$120.83	$120.85	$120.80
7 purchase totals =	$970.82		$1,057.3127	$1,057.31	$1,057.35	$1,057.20