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	$212.55	3.266%	$219.4919	$219.49	$219.50	$219.50
Purchase #2	$87.48	3.232%	$90.3074	$90.31	$90.30	$90.30
Purchase #3	$249.54	5.656%	$263.654	$263.65	$263.65	$263.70
Purchase #4	$160.33	9.430%	$175.4491	$175.45	$175.45	$175.40
Purchase #5	$39.49	6.364%	$42.0031	$42.00	$42.00	$42.00
Purchase #6	$24.70	3.489%	$25.5618	$25.56	$25.55	$25.60
Purchase #7	$205.81	12.654%	$231.8532	$231.85	$231.85	$231.90
7 purchase totals =	$979.90		$1,048.3205	$1,048.31	$1,048.30	$1,048.40