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	$149.62	9.819%	$164.3112	$164.31	$164.30	$164.30
Purchase #2	$237.72	5.364%	$250.4713	$250.47	$250.45	$250.50
Purchase #3	$191.80	10.319%	$211.5918	$211.59	$211.60	$211.60
Purchase #4	$145.89	7.803%	$157.2738	$157.27	$157.25	$157.30
Purchase #5	$73.28	11.701%	$81.8545	$81.85	$81.85	$81.90
Purchase #6	$191.56	13.538%	$217.4934	$217.49	$217.50	$217.50
Purchase #7	$18.59	10.256%	$20.4966	$20.50	$20.50	$20.50
7 purchase totals =	$1,008.46		$1,103.4926	$1,103.48	$1,103.45	$1,103.60