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	$64.95	6.780%	$69.3536	$69.35	$69.35	$69.40
Purchase #2	$30.30	11.418%	$33.7597	$33.76	$33.75	$33.80
Purchase #3	$32.87	13.427%	$37.2835	$37.28	$37.30	$37.30
Purchase #4	$131.45	9.656%	$144.1428	$144.14	$144.15	$144.10
Purchase #5	$90.53	11.705%	$101.1265	$101.13	$101.15	$101.10
Purchase #6	$113.85	8.631%	$123.6764	$123.68	$123.70	$123.70
Purchase #7	$150.92	13.329%	$171.0361	$171.04	$171.05	$171.00
7 purchase totals =	$614.87		$680.3786	$680.38	$680.45	$680.40