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	$63.71	5.874%	$67.4523	$67.45	$67.45	$67.50
Purchase #2	$194.60	11.164%	$216.3251	$216.33	$216.35	$216.30
Purchase #3	$188.52	4.663%	$197.3107	$197.31	$197.30	$197.30
Purchase #4	$219.96	13.720%	$250.1385	$250.14	$250.15	$250.10
Purchase #5	$41.86	4.657%	$43.8094	$43.81	$43.80	$43.80
Purchase #6	$144.94	8.274%	$156.9323	$156.93	$156.95	$156.90
Purchase #7	$163.81	11.358%	$182.4155	$182.42	$182.40	$182.40
7 purchase totals =	$1,017.40		$1,114.3838	$1,114.39	$1,114.40	$1,114.30