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	$209.26	4.359%	$218.3816	$218.38	$218.40	$218.40
Purchase #2	$96.87	7.415%	$104.0529	$104.05	$104.05	$104.10
Purchase #3	$43.39	7.434%	$46.6156	$46.62	$46.60	$46.60
Purchase #4	$30.89	3.332%	$31.9193	$31.92	$31.90	$31.90
Purchase #5	$233.73	5.450%	$246.4683	$246.47	$246.45	$246.50
Purchase #6	$62.88	7.463%	$67.5727	$67.57	$67.55	$67.60
Purchase #7	$76.68	12.740%	$86.449	$86.45	$86.45	$86.40
7 purchase totals =	$753.70		$801.4594	$801.46	$801.40	$801.50