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	$128.41	7.120%	$137.5528	$137.55	$137.55	$137.60
Purchase #2	$12.53	12.234%	$14.0629	$14.06	$14.05	$14.10
Purchase #3	$224.87	7.410%	$241.5329	$241.53	$241.55	$241.50
Purchase #4	$182.34	12.109%	$204.4196	$204.42	$204.40	$204.40
Purchase #5	$136.96	13.448%	$155.3784	$155.38	$155.40	$155.40
Purchase #6	$78.85	13.496%	$89.4916	$89.49	$89.50	$89.50
Purchase #7	$238.66	8.650%	$259.3041	$259.30	$259.30	$259.30
7 purchase totals =	$1,002.62		$1,101.7423	$1,101.73	$1,101.75	$1,101.80