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	$76.79	8.476%	$83.2987	$83.30	$83.30	$83.30
Purchase #2	$94.92	6.150%	$100.7576	$100.76	$100.75	$100.80
Purchase #3	$77.66	6.815%	$82.9525	$82.95	$82.95	$83.00
Purchase #4	$165.48	12.497%	$186.16	$186.16	$186.15	$186.20
Purchase #5	$231.83	3.279%	$239.4317	$239.43	$239.45	$239.40
Purchase #6	$48.92	3.111%	$50.4419	$50.44	$50.45	$50.40
Purchase #7	$139.93	4.547%	$146.2926	$146.29	$146.30	$146.30
7 purchase totals =	$835.53		$889.3350	$889.33	$889.35	$889.40