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	$31.32	13.420%	$35.5231	$35.52	$35.50	$35.50
Purchase #2	$132.89	12.690%	$149.7537	$149.75	$149.75	$149.80
Purchase #3	$101.66	7.659%	$109.4461	$109.45	$109.45	$109.40
Purchase #4	$207.88	3.197%	$214.5259	$214.53	$214.55	$214.50
Purchase #5	$89.37	4.687%	$93.5588	$93.56	$93.55	$93.60
Purchase #6	$230.46	11.740%	$257.516	$257.52	$257.50	$257.50
Purchase #7	$148.66	5.113%	$156.261	$156.26	$156.25	$156.30
7 purchase totals =	$942.24		$1,016.5846	$1,016.59	$1,016.55	$1,016.60