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	$80.94	6.397%	$86.1177	$86.12	$86.10	$86.10
Purchase #2	$152.61	10.160%	$168.1152	$168.12	$168.10	$168.10
Purchase #3	$62.73	7.626%	$67.5138	$67.51	$67.50	$67.50
Purchase #4	$45.30	3.129%	$46.7174	$46.72	$46.70	$46.70
Purchase #5	$102.51	13.448%	$116.2955	$116.30	$116.30	$116.30
Purchase #6	$96.47	5.238%	$101.5231	$101.52	$101.50	$101.50
Purchase #7	$173.48	7.389%	$186.2984	$186.30	$186.30	$186.30
7 purchase totals =	$714.04		$772.5811	$772.59	$772.50	$772.50