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	$80.39	13.146%	$90.9581	$90.96	$90.95	$91.00
Purchase #2	$108.32	5.120%	$113.866	$113.87	$113.85	$113.90
Purchase #3	$195.64	5.492%	$206.3845	$206.38	$206.40	$206.40
Purchase #4	$45.97	9.586%	$50.3767	$50.38	$50.40	$50.40
Purchase #5	$236.82	11.506%	$264.0685	$264.07	$264.05	$264.10
Purchase #6	$174.44	10.590%	$192.9132	$192.91	$192.90	$192.90
Purchase #7	$137.34	4.678%	$143.7648	$143.76	$143.75	$143.80
7 purchase totals =	$978.92		$1,062.3318	$1,062.33	$1,062.30	$1,062.50