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	$79.54	5.440%	$83.867	$83.87	$83.85	$83.90
Purchase #2	$26.37	5.752%	$27.8868	$27.89	$27.90	$27.90
Purchase #3	$134.56	11.651%	$150.2376	$150.24	$150.25	$150.20
Purchase #4	$99.54	5.148%	$104.6643	$104.66	$104.65	$104.70
Purchase #5	$56.68	13.313%	$64.2258	$64.23	$64.25	$64.20
Purchase #6	$121.28	12.518%	$136.4618	$136.46	$136.45	$136.50
Purchase #7	$104.56	11.343%	$116.4202	$116.42	$116.40	$116.40
7 purchase totals =	$622.53		$683.7635	$683.77	$683.75	$683.80