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	$82.80	13.818%	$94.2413	$94.24	$94.25	$94.20
Purchase #2	$190.47	3.130%	$196.4317	$196.43	$196.45	$196.40
Purchase #3	$86.39	11.401%	$96.2393	$96.24	$96.25	$96.20
Purchase #4	$52.55	5.306%	$55.3383	$55.34	$55.35	$55.30
Purchase #5	$57.73	10.123%	$63.574	$63.57	$63.55	$63.60
Purchase #6	$103.62	5.497%	$109.316	$109.32	$109.30	$109.30
Purchase #7	$199.63	8.259%	$216.1174	$216.12	$216.10	$216.10
7 purchase totals =	$773.19		$831.2580	$831.26	$831.25	$831.10