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	$119.66	3.321%	$123.6339	$123.63	$123.65	$123.60
Purchase #2	$86.35	10.343%	$95.2812	$95.28	$95.30	$95.30
Purchase #3	$151.78	3.423%	$156.9754	$156.98	$157.00	$157.00
Purchase #4	$157.55	13.512%	$178.8382	$178.84	$178.85	$178.80
Purchase #5	$122.26	10.307%	$134.8613	$134.86	$134.85	$134.90
Purchase #6	$246.65	3.414%	$255.0706	$255.07	$255.05	$255.10
Purchase #7	$188.40	6.426%	$200.5066	$200.51	$200.50	$200.50
7 purchase totals =	$1,072.65		$1,145.1672	$1,145.17	$1,145.20	$1,145.20