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	$54.72	11.577%	$61.0549	$61.05	$61.05	$61.10
Purchase #2	$54.86	8.270%	$59.3969	$59.40	$59.40	$59.40
Purchase #3	$77.92	10.272%	$85.9239	$85.92	$85.90	$85.90
Purchase #4	$43.58	3.604%	$45.1506	$45.15	$45.15	$45.20
Purchase #5	$140.61	7.576%	$151.2626	$151.26	$151.25	$151.30
Purchase #6	$16.64	13.171%	$18.8317	$18.83	$18.85	$18.80
Purchase #7	$7.91	8.842%	$8.6094	$8.61	$8.60	$8.60
7 purchase totals =	$396.24		$430.2300	$430.22	$430.20	$430.30