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	$139.51	4.835%	$146.2553	$146.26	$146.25	$146.30
Purchase #2	$233.39	4.559%	$244.0303	$244.03	$244.05	$244.00
Purchase #3	$142.32	10.105%	$156.7014	$156.70	$156.70	$156.70
Purchase #4	$91.80	8.790%	$99.8692	$99.87	$99.85	$99.90
Purchase #5	$74.44	8.168%	$80.5203	$80.52	$80.50	$80.50
Purchase #6	$142.48	4.384%	$148.7263	$148.73	$148.75	$148.70
Purchase #7	$202.75	3.831%	$210.5174	$210.52	$210.50	$210.50
7 purchase totals =	$1,026.69		$1,086.6202	$1,086.63	$1,086.60	$1,086.60