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	$50.92	13.103%	$57.592	$57.59	$57.60	$57.60
Purchase #2	$52.60	12.174%	$59.0035	$59.00	$59.00	$59.00
Purchase #3	$193.71	11.741%	$216.4535	$216.45	$216.45	$216.50
Purchase #4	$50.71	10.753%	$56.1628	$56.16	$56.15	$56.20
Purchase #5	$196.82	9.535%	$215.5868	$215.59	$215.60	$215.60
Purchase #6	$165.46	12.304%	$185.8182	$185.82	$185.80	$185.80
Purchase #7	$92.64	3.730%	$96.0955	$96.10	$96.10	$96.10
7 purchase totals =	$802.86		$886.7123	$886.71	$886.70	$886.80