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	$83.33	7.242%	$89.3648	$89.36	$89.35	$89.40
Purchase #2	$57.38	11.277%	$63.8507	$63.85	$63.85	$63.90
Purchase #3	$201.41	4.187%	$209.843	$209.84	$209.85	$209.80
Purchase #4	$28.57	4.264%	$29.7882	$29.79	$29.80	$29.80
Purchase #5	$167.53	3.188%	$172.8709	$172.87	$172.85	$172.90
Purchase #6	$229.61	8.635%	$249.4368	$249.44	$249.45	$249.40
Purchase #7	$247.39	13.452%	$280.6689	$280.67	$280.65	$280.70
7 purchase totals =	$1,015.22		$1,095.8233	$1,095.82	$1,095.80	$1,095.90