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	$71.94	10.605%	$79.5692	$79.57	$79.55	$79.60
Purchase #2	$116.38	6.144%	$123.5304	$123.53	$123.55	$123.50
Purchase #3	$56.77	6.700%	$60.5736	$60.57	$60.55	$60.60
Purchase #4	$24.42	5.424%	$25.7445	$25.74	$25.75	$25.70
Purchase #5	$223.49	6.543%	$238.113	$238.11	$238.10	$238.10
Purchase #6	$100.29	11.204%	$111.5265	$111.53	$111.55	$111.50
Purchase #7	$232.64	11.368%	$259.0865	$259.09	$259.10	$259.10
7 purchase totals =	$825.93		$898.1437	$898.14	$898.15	$898.10