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	$168.40	4.449%	$175.8921	$175.89	$175.90	$175.90
Purchase #2	$89.45	11.310%	$99.5668	$99.57	$99.55	$99.60
Purchase #3	$59.48	13.865%	$67.7269	$67.73	$67.75	$67.70
Purchase #4	$222.50	8.247%	$240.8496	$240.85	$240.85	$240.80
Purchase #5	$159.88	5.646%	$168.9068	$168.91	$168.90	$168.90
Purchase #6	$192.64	4.449%	$201.2106	$201.21	$201.20	$201.20
Purchase #7	$20.47	11.709%	$22.8668	$22.87	$22.85	$22.90
7 purchase totals =	$912.82		$977.0196	$977.03	$977.00	$977.00