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	$174.25	4.509%	$182.1069	$182.11	$182.10	$182.10
Purchase #2	$139.87	5.402%	$147.4258	$147.43	$147.45	$147.40
Purchase #3	$203.91	3.221%	$210.4779	$210.48	$210.50	$210.50
Purchase #4	$78.88	8.272%	$85.405	$85.41	$85.40	$85.40
Purchase #5	$82.93	8.669%	$90.1192	$90.12	$90.10	$90.10
Purchase #6	$72.65	13.108%	$82.173	$82.17	$82.15	$82.20
Purchase #7	$104.41	11.778%	$116.7074	$116.71	$116.70	$116.70
7 purchase totals =	$856.90		$914.4152	$914.43	$914.40	$914.40