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	$167.42	5.521%	$176.6633	$176.66	$176.65	$176.70
Purchase #2	$69.67	12.698%	$78.5167	$78.52	$78.50	$78.50
Purchase #3	$87.76	3.459%	$90.7956	$90.80	$90.80	$90.80
Purchase #4	$29.49	5.166%	$31.0135	$31.01	$31.00	$31.00
Purchase #5	$174.39	11.415%	$194.2966	$194.30	$194.30	$194.30
Purchase #6	$178.86	6.256%	$190.0495	$190.05	$190.05	$190.00
Purchase #7	$141.96	6.818%	$151.6388	$151.64	$151.65	$151.60
7 purchase totals =	$849.55		$912.9740	$912.98	$912.95	$912.90