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	$236.39	5.136%	$248.531	$248.53	$248.55	$248.50
Purchase #2	$95.72	9.305%	$104.6267	$104.63	$104.65	$104.60
Purchase #3	$112.96	9.644%	$123.8539	$123.85	$123.85	$123.90
Purchase #4	$88.42	3.587%	$91.5916	$91.59	$91.60	$91.60
Purchase #5	$229.40	6.519%	$244.3546	$244.35	$244.35	$244.40
Purchase #6	$79.74	7.643%	$85.8345	$85.83	$85.85	$85.80
Purchase #7	$222.50	12.395%	$250.0789	$250.08	$250.10	$250.10
7 purchase totals =	$1,065.13		$1,148.8712	$1,148.86	$1,148.95	$1,148.90