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	$41.30	12.594%	$46.5013	$46.50	$46.50	$46.50
Purchase #2	$116.45	10.292%	$128.435	$128.44	$128.45	$128.40
Purchase #3	$144.93	5.326%	$152.649	$152.65	$152.65	$152.60
Purchase #4	$245.37	3.747%	$254.564	$254.56	$254.55	$254.60
Purchase #5	$192.89	13.307%	$218.5579	$218.56	$218.55	$218.60
Purchase #6	$200.73	7.182%	$215.1464	$215.15	$215.15	$215.10
Purchase #7	$144.29	7.139%	$154.5909	$154.59	$154.60	$154.60
7 purchase totals =	$1,085.96		$1,170.4445	$1,170.45	$1,170.45	$1,170.40