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	$215.93	5.532%	$227.8752	$227.88	$227.90	$227.90
Purchase #2	$172.77	7.817%	$186.2754	$186.28	$186.30	$186.30
Purchase #3	$70.69	9.731%	$77.5688	$77.57	$77.55	$77.60
Purchase #4	$92.42	13.190%	$104.6102	$104.61	$104.60	$104.60
Purchase #5	$179.59	3.286%	$185.4913	$185.49	$185.50	$185.50
Purchase #6	$183.44	4.585%	$191.8507	$191.85	$191.85	$191.90
Purchase #7	$166.38	7.841%	$179.4259	$179.43	$179.45	$179.40
7 purchase totals =	$1,081.22		$1,153.0975	$1,153.11	$1,153.15	$1,153.20