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	$69.54	13.389%	$78.8507	$78.85	$78.85	$78.90
Purchase #2	$75.84	4.709%	$79.4113	$79.41	$79.40	$79.40
Purchase #3	$231.43	4.382%	$241.5713	$241.57	$241.55	$241.60
Purchase #4	$203.80	12.285%	$228.8368	$228.84	$228.85	$228.80
Purchase #5	$238.80	11.658%	$266.6393	$266.64	$266.65	$266.60
Purchase #6	$28.86	10.408%	$31.8637	$31.86	$31.85	$31.90
Purchase #7	$105.40	12.513%	$118.5887	$118.59	$118.60	$118.60
7 purchase totals =	$953.67		$1,045.7618	$1,045.76	$1,045.75	$1,045.80