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	$148.71	12.765%	$167.6928	$167.69	$167.70	$167.70
Purchase #2	$160.67	6.651%	$171.3562	$171.36	$171.35	$171.40
Purchase #3	$73.83	12.116%	$82.7752	$82.78	$82.80	$82.80
Purchase #4	$192.86	6.687%	$205.7565	$205.76	$205.75	$205.80
Purchase #5	$99.93	8.366%	$108.2901	$108.29	$108.30	$108.30
Purchase #6	$24.86	4.336%	$25.9379	$25.94	$25.95	$25.90
Purchase #7	$32.60	9.287%	$35.6276	$35.63	$35.65	$35.60
7 purchase totals =	$733.46		$797.4363	$797.45	$797.50	$797.50