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	$65.59	10.627%	$72.5602	$72.56	$72.55	$72.60
Purchase #2	$28.92	6.277%	$30.7353	$30.74	$30.75	$30.70
Purchase #3	$99.63	13.850%	$113.4288	$113.43	$113.45	$113.40
Purchase #4	$79.45	12.363%	$89.2724	$89.27	$89.25	$89.30
Purchase #5	$102.75	10.578%	$113.6189	$113.62	$113.60	$113.60
Purchase #6	$206.68	11.807%	$231.0827	$231.08	$231.10	$231.10
Purchase #7	$198.67	5.745%	$210.0836	$210.08	$210.10	$210.10
7 purchase totals =	$781.69		$860.7819	$860.78	$860.80	$860.80