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	$133.47	9.407%	$146.0255	$146.03	$146.05	$146.00
Purchase #2	$13.34	4.273%	$13.91	$13.91	$13.90	$13.90
Purchase #3	$83.36	7.782%	$89.8471	$89.85	$89.85	$89.80
Purchase #4	$82.28	7.408%	$88.3753	$88.38	$88.40	$88.40
Purchase #5	$185.31	7.346%	$198.9229	$198.92	$198.90	$198.90
Purchase #6	$40.87	7.797%	$44.0566	$44.06	$44.05	$44.10
Purchase #7	$5.83	4.491%	$6.0918	$6.09	$6.10	$6.10
7 purchase totals =	$544.46		$587.2292	$587.24	$587.25	$587.20