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	$212.86	13.326%	$241.2257	$241.23	$241.25	$241.20
Purchase #2	$158.69	13.845%	$180.6606	$180.66	$180.65	$180.70
Purchase #3	$55.53	11.444%	$61.8849	$61.88	$61.90	$61.90
Purchase #4	$128.61	10.754%	$142.4407	$142.44	$142.45	$142.40
Purchase #5	$6.40	3.251%	$6.6081	$6.61	$6.60	$6.60
Purchase #6	$128.93	12.697%	$145.3002	$145.30	$145.30	$145.30
Purchase #7	$185.36	12.482%	$208.4966	$208.50	$208.50	$208.50
7 purchase totals =	$876.38		$986.6168	$986.62	$986.65	$986.60