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	$51.77	12.267%	$58.1206	$58.12	$58.10	$58.10
Purchase #2	$231.72	13.172%	$262.2422	$262.24	$262.25	$262.20
Purchase #3	$184.48	13.180%	$208.7945	$208.79	$208.80	$208.80
Purchase #4	$122.43	12.179%	$137.3407	$137.34	$137.35	$137.30
Purchase #5	$128.34	11.623%	$143.257	$143.26	$143.25	$143.30
Purchase #6	$93.31	6.734%	$99.5935	$99.59	$99.60	$99.60
Purchase #7	$148.42	12.328%	$166.7172	$166.72	$166.70	$166.70
7 purchase totals =	$960.47		$1,076.0657	$1,076.06	$1,076.05	$1,076.00