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	$82.49	9.673%	$90.4693	$90.47	$90.45	$90.50
Purchase #2	$191.28	9.392%	$209.245	$209.25	$209.25	$209.20
Purchase #3	$6.76	10.659%	$7.4805	$7.48	$7.50	$7.50
Purchase #4	$229.65	10.301%	$253.3062	$253.31	$253.30	$253.30
Purchase #5	$122.89	3.506%	$127.1985	$127.20	$127.20	$127.20
Purchase #6	$206.48	9.483%	$226.0605	$226.06	$226.05	$226.10
Purchase #7	$205.77	6.241%	$218.6121	$218.61	$218.60	$218.60
7 purchase totals =	$1,045.32		$1,132.3721	$1,132.38	$1,132.35	$1,132.40