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	$79.75	8.426%	$86.4697	$86.47	$86.45	$86.50
Purchase #2	$222.58	10.156%	$245.1852	$245.19	$245.20	$245.20
Purchase #3	$10.90	8.147%	$11.788	$11.79	$11.80	$11.80
Purchase #4	$82.35	8.632%	$89.4585	$89.46	$89.45	$89.50
Purchase #5	$77.27	4.192%	$80.5092	$80.51	$80.50	$80.50
Purchase #6	$5.52	11.128%	$6.1343	$6.13	$6.15	$6.10
Purchase #7	$147.32	7.281%	$158.0464	$158.05	$158.05	$158.00
7 purchase totals =	$625.69		$677.5913	$677.60	$677.60	$677.60