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	$54.31	9.492%	$59.4651	$59.47	$59.45	$59.50
Purchase #2	$206.51	9.380%	$225.8806	$225.88	$225.90	$225.90
Purchase #3	$192.93	7.450%	$207.3033	$207.30	$207.30	$207.30
Purchase #4	$79.87	12.191%	$89.607	$89.61	$89.60	$89.60
Purchase #5	$117.84	9.658%	$129.221	$129.22	$129.20	$129.20
Purchase #6	$143.83	8.372%	$155.8714	$155.87	$155.85	$155.90
Purchase #7	$150.74	11.698%	$168.3736	$168.37	$168.35	$168.40
7 purchase totals =	$946.03		$1,035.7220	$1,035.72	$1,035.65	$1,035.80