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	$184.34	12.727%	$207.801	$207.80	$207.80	$207.80
Purchase #2	$9.40	9.757%	$10.3172	$10.32	$10.30	$10.30
Purchase #3	$86.32	9.457%	$94.4833	$94.48	$94.50	$94.50
Purchase #4	$169.85	3.364%	$175.5638	$175.56	$175.55	$175.60
Purchase #5	$56.25	9.762%	$61.7411	$61.74	$61.75	$61.70
Purchase #6	$38.84	9.515%	$42.5356	$42.54	$42.55	$42.50
Purchase #7	$63.82	10.435%	$70.4796	$70.48	$70.50	$70.50
7 purchase totals =	$608.82		$662.9216	$662.92	$662.95	$662.90