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	$175.36	5.408%	$184.8435	$184.84	$184.85	$184.80
Purchase #2	$94.92	4.400%	$99.0965	$99.10	$99.10	$99.10
Purchase #3	$77.56	3.432%	$80.2219	$80.22	$80.20	$80.20
Purchase #4	$76.72	13.349%	$86.9614	$86.96	$86.95	$87.00
Purchase #5	$38.82	4.494%	$40.5646	$40.56	$40.55	$40.60
Purchase #6	$74.29	6.256%	$78.9376	$78.94	$78.95	$78.90
Purchase #7	$149.34	8.412%	$161.9025	$161.90	$161.90	$161.90
7 purchase totals =	$687.01		$732.5280	$732.52	$732.50	$732.50