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	$198.77	3.825%	$206.373	$206.37	$206.35	$206.40
Purchase #2	$77.59	10.211%	$85.5127	$85.51	$85.50	$85.50
Purchase #3	$240.58	4.179%	$250.6338	$250.63	$250.65	$250.60
Purchase #4	$241.57	5.753%	$255.4675	$255.47	$255.45	$255.50
Purchase #5	$80.64	7.280%	$86.5106	$86.51	$86.50	$86.50
Purchase #6	$227.50	3.486%	$235.4307	$235.43	$235.45	$235.40
Purchase #7	$21.72	10.735%	$24.0516	$24.05	$24.05	$24.10
7 purchase totals =	$1,088.37		$1,143.9799	$1,143.97	$1,143.95	$1,144.00