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	$192.35	7.864%	$207.4764	$207.48	$207.50	$207.50
Purchase #2	$56.96	4.242%	$59.3762	$59.38	$59.40	$59.40
Purchase #3	$11.55	11.690%	$12.9002	$12.90	$12.90	$12.90
Purchase #4	$126.73	8.326%	$137.2815	$137.28	$137.30	$137.30
Purchase #5	$63.78	4.704%	$66.7802	$66.78	$66.80	$66.80
Purchase #6	$200.30	5.411%	$211.1382	$211.14	$211.15	$211.10
Purchase #7	$11.28	9.437%	$12.3445	$12.34	$12.35	$12.30
7 purchase totals =	$662.95		$707.2972	$707.30	$707.40	$707.30