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	$245.93	5.533%	$259.5373	$259.54	$259.55	$259.50
Purchase #2	$55.75	6.392%	$59.3135	$59.31	$59.30	$59.30
Purchase #3	$83.97	10.417%	$92.7172	$92.72	$92.70	$92.70
Purchase #4	$117.38	7.504%	$126.1882	$126.19	$126.20	$126.20
Purchase #5	$216.27	5.345%	$227.8296	$227.83	$227.85	$227.80
Purchase #6	$236.65	4.472%	$247.233	$247.23	$247.25	$247.20
Purchase #7	$109.73	8.241%	$118.7728	$118.77	$118.75	$118.80
7 purchase totals =	$1,065.68		$1,131.5916	$1,131.59	$1,131.60	$1,131.50