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	$90.59	11.440%	$100.9535	$100.95	$100.95	$101.00
Purchase #2	$245.77	12.846%	$277.3416	$277.34	$277.35	$277.30
Purchase #3	$203.56	12.136%	$228.264	$228.26	$228.25	$228.30
Purchase #4	$66.38	5.111%	$69.7727	$69.77	$69.75	$69.80
Purchase #5	$131.39	11.354%	$146.308	$146.31	$146.30	$146.30
Purchase #6	$197.77	12.534%	$222.5585	$222.56	$222.55	$222.60
Purchase #7	$35.64	11.819%	$39.8523	$39.85	$39.85	$39.90
7 purchase totals =	$971.10		$1,085.0506	$1,085.04	$1,085.00	$1,085.20