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	$82.47	10.229%	$90.9059	$90.91	$90.90	$90.90
Purchase #2	$12.83	13.827%	$14.604	$14.60	$14.60	$14.60
Purchase #3	$154.33	8.813%	$167.9311	$167.93	$167.95	$167.90
Purchase #4	$173.29	6.405%	$184.3892	$184.39	$184.40	$184.40
Purchase #5	$133.29	5.710%	$140.9009	$140.90	$140.90	$140.90
Purchase #6	$92.30	3.647%	$95.6662	$95.67	$95.65	$95.70
Purchase #7	$235.72	13.235%	$266.9175	$266.92	$266.90	$266.90
7 purchase totals =	$884.23		$961.3148	$961.32	$961.30	$961.30