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	$193.30	7.680%	$208.1454	$208.15	$208.15	$208.10
Purchase #2	$49.67	13.514%	$56.3824	$56.38	$56.40	$56.40
Purchase #3	$79.51	3.614%	$82.3835	$82.38	$82.40	$82.40
Purchase #4	$29.48	8.848%	$32.0884	$32.09	$32.10	$32.10
Purchase #5	$174.60	4.531%	$182.5111	$182.51	$182.50	$182.50
Purchase #6	$185.65	3.259%	$191.7003	$191.70	$191.70	$191.70
Purchase #7	$193.74	3.616%	$200.7456	$200.75	$200.75	$200.70
7 purchase totals =	$905.95		$953.9567	$953.96	$954.00	$953.90