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	$74.32	9.839%	$81.6323	$81.63	$81.65	$81.60
Purchase #2	$240.98	11.465%	$268.6084	$268.61	$268.60	$268.60
Purchase #3	$159.85	3.471%	$165.3984	$165.40	$165.40	$165.40
Purchase #4	$250.46	3.151%	$258.352	$258.35	$258.35	$258.40
Purchase #5	$99.48	12.467%	$111.8822	$111.88	$111.90	$111.90
Purchase #6	$194.57	9.707%	$213.4569	$213.46	$213.45	$213.50
Purchase #7	$9.79	13.735%	$11.1347	$11.13	$11.15	$11.10
7 purchase totals =	$1,029.45		$1,110.4649	$1,110.46	$1,110.50	$1,110.50