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	$133.54	4.410%	$139.4291	$139.43	$139.45	$139.40
Purchase #2	$86.58	12.592%	$97.4822	$97.48	$97.50	$97.50
Purchase #3	$151.26	9.520%	$165.66	$165.66	$165.65	$165.70
Purchase #4	$89.77	11.186%	$99.8117	$99.81	$99.80	$99.80
Purchase #5	$152.79	12.519%	$171.9178	$171.92	$171.90	$171.90
Purchase #6	$182.56	3.573%	$189.0829	$189.08	$189.10	$189.10
Purchase #7	$199.85	11.256%	$222.3451	$222.35	$222.35	$222.30
7 purchase totals =	$996.35		$1,085.7288	$1,085.73	$1,085.75	$1,085.70