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	$57.76	13.842%	$65.7551	$65.76	$65.75	$65.80
Purchase #2	$19.37	7.658%	$20.8534	$20.85	$20.85	$20.90
Purchase #3	$191.96	8.801%	$208.8544	$208.85	$208.85	$208.90
Purchase #4	$19.40	3.561%	$20.0908	$20.09	$20.10	$20.10
Purchase #5	$74.97	9.804%	$82.3201	$82.32	$82.30	$82.30
Purchase #6	$112.31	3.334%	$116.0544	$116.05	$116.05	$116.10
Purchase #7	$39.56	5.572%	$41.7643	$41.76	$41.75	$41.80
7 purchase totals =	$515.33		$555.6925	$555.68	$555.65	$555.90