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	$107.54	4.435%	$112.3094	$112.31	$112.30	$112.30
Purchase #2	$83.45	5.607%	$88.129	$88.13	$88.15	$88.10
Purchase #3	$143.71	6.422%	$152.9391	$152.94	$152.95	$152.90
Purchase #4	$164.79	8.341%	$178.5351	$178.54	$178.55	$178.50
Purchase #5	$208.89	6.864%	$223.2282	$223.23	$223.25	$223.20
Purchase #6	$100.43	12.158%	$112.6403	$112.64	$112.65	$112.60
Purchase #7	$219.96	11.774%	$245.8581	$245.86	$245.85	$245.90
7 purchase totals =	$1,028.77		$1,113.6392	$1,113.65	$1,113.70	$1,113.50