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	$82.86	10.230%	$91.3366	$91.34	$91.35	$91.30
Purchase #2	$219.41	3.706%	$227.5413	$227.54	$227.55	$227.50
Purchase #3	$55.35	6.350%	$58.8647	$58.86	$58.85	$58.90
Purchase #4	$25.40	7.276%	$27.2481	$27.25	$27.25	$27.20
Purchase #5	$199.44	3.121%	$205.6645	$205.66	$205.65	$205.70
Purchase #6	$52.78	11.828%	$59.0228	$59.02	$59.00	$59.00
Purchase #7	$72.98	13.651%	$82.9425	$82.94	$82.95	$82.90
7 purchase totals =	$708.22		$752.6205	$752.61	$752.60	$752.50