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	$174.63	12.712%	$196.829	$196.83	$196.85	$196.80
Purchase #2	$111.74	12.646%	$125.8706	$125.87	$125.85	$125.90
Purchase #3	$159.37	9.314%	$174.2137	$174.21	$174.20	$174.20
Purchase #4	$151.77	5.830%	$160.6182	$160.62	$160.60	$160.60
Purchase #5	$131.44	11.236%	$146.2086	$146.21	$146.20	$146.20
Purchase #6	$27.58	10.433%	$30.4574	$30.46	$30.45	$30.50
Purchase #7	$94.25	4.250%	$98.2556	$98.26	$98.25	$98.30
7 purchase totals =	$850.78		$932.4531	$932.46	$932.40	$932.50