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	$185.77	4.341%	$193.8343	$193.83	$193.85	$193.80
Purchase #2	$250.27	7.329%	$268.6123	$268.61	$268.60	$268.60
Purchase #3	$95.68	5.194%	$100.6496	$100.65	$100.65	$100.60
Purchase #4	$61.91	8.833%	$67.3785	$67.38	$67.40	$67.40
Purchase #5	$234.79	12.581%	$264.3289	$264.33	$264.35	$264.30
Purchase #6	$206.61	6.252%	$219.5273	$219.53	$219.55	$219.50
Purchase #7	$44.75	6.720%	$47.7572	$47.76	$47.75	$47.80
7 purchase totals =	$1,079.78		$1,162.0881	$1,162.09	$1,162.15	$1,162.00