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	$50.46	8.683%	$54.8414	$54.84	$54.85	$54.80
Purchase #2	$212.51	8.708%	$231.0154	$231.02	$231.00	$231.00
Purchase #3	$230.59	3.264%	$238.1165	$238.12	$238.10	$238.10
Purchase #4	$33.48	11.427%	$37.3058	$37.31	$37.30	$37.30
Purchase #5	$136.26	10.830%	$151.017	$151.02	$151.00	$151.00
Purchase #6	$155.56	10.533%	$171.9451	$171.95	$171.95	$171.90
Purchase #7	$142.40	9.844%	$156.4179	$156.42	$156.40	$156.40
7 purchase totals =	$961.26		$1,040.6591	$1,040.68	$1,040.60	$1,040.50