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	$51.65	4.380%	$53.9123	$53.91	$53.90	$53.90
Purchase #2	$245.54	4.362%	$256.2505	$256.25	$256.25	$256.30
Purchase #3	$215.54	9.219%	$235.4106	$235.41	$235.40	$235.40
Purchase #4	$229.79	5.111%	$241.5346	$241.53	$241.55	$241.50
Purchase #5	$178.42	10.706%	$197.5216	$197.52	$197.50	$197.50
Purchase #6	$129.52	11.223%	$144.056	$144.06	$144.05	$144.10
Purchase #7	$36.52	5.634%	$38.5775	$38.58	$38.60	$38.60
7 purchase totals =	$1,086.98		$1,167.2631	$1,167.26	$1,167.25	$1,167.30