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	$199.47	3.705%	$206.8604	$206.86	$206.85	$206.90
Purchase #2	$111.60	6.115%	$118.4243	$118.42	$118.40	$118.40
Purchase #3	$143.50	3.753%	$148.8856	$148.89	$148.90	$148.90
Purchase #4	$6.71	5.148%	$7.0554	$7.06	$7.05	$7.10
Purchase #5	$18.48	11.127%	$20.5363	$20.54	$20.55	$20.50
Purchase #6	$67.73	4.246%	$70.6058	$70.61	$70.60	$70.60
Purchase #7	$123.49	9.152%	$134.7918	$134.79	$134.80	$134.80
7 purchase totals =	$670.98		$707.1596	$707.17	$707.15	$707.20