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	$154.27	10.530%	$170.5146	$170.51	$170.50	$170.50
Purchase #2	$70.28	9.126%	$76.6938	$76.69	$76.70	$76.70
Purchase #3	$81.54	6.107%	$86.5196	$86.52	$86.50	$86.50
Purchase #4	$174.53	6.865%	$186.5115	$186.51	$186.50	$186.50
Purchase #5	$35.90	7.826%	$38.7095	$38.71	$38.70	$38.70
Purchase #6	$208.36	5.157%	$219.1051	$219.11	$219.10	$219.10
Purchase #7	$55.71	6.772%	$59.4827	$59.48	$59.50	$59.50
7 purchase totals =	$780.59		$837.5368	$837.53	$837.50	$837.50