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	$113.51	8.414%	$123.0607	$123.06	$123.05	$123.10
Purchase #2	$136.85	8.653%	$148.6916	$148.69	$148.70	$148.70
Purchase #3	$90.57	4.393%	$94.5487	$94.55	$94.55	$94.50
Purchase #4	$74.35	11.301%	$82.7523	$82.75	$82.75	$82.80
Purchase #5	$13.46	3.194%	$13.8899	$13.89	$13.90	$13.90
Purchase #6	$231.28	9.634%	$253.5615	$253.56	$253.55	$253.60
Purchase #7	$190.77	9.678%	$209.2327	$209.23	$209.25	$209.20
7 purchase totals =	$850.79		$925.7374	$925.73	$925.75	$925.80