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	$91.56	13.378%	$103.8089	$103.81	$103.80	$103.80
Purchase #2	$128.67	12.172%	$144.3317	$144.33	$144.35	$144.30
Purchase #3	$240.57	9.542%	$263.5252	$263.53	$263.55	$263.50
Purchase #4	$201.51	10.334%	$222.334	$222.33	$222.35	$222.30
Purchase #5	$237.81	5.160%	$250.081	$250.08	$250.10	$250.10
Purchase #6	$12.44	10.371%	$13.7302	$13.73	$13.75	$13.70
Purchase #7	$26.63	3.787%	$27.6385	$27.64	$27.65	$27.60
7 purchase totals =	$939.19		$1,025.4495	$1,025.45	$1,025.55	$1,025.30