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	$133.85	5.601%	$141.3469	$141.35	$141.35	$141.30
Purchase #2	$116.71	10.404%	$128.8525	$128.85	$128.85	$128.90
Purchase #3	$14.67	8.347%	$15.8945	$15.89	$15.90	$15.90
Purchase #4	$72.62	9.352%	$79.4114	$79.41	$79.40	$79.40
Purchase #5	$164.43	4.268%	$171.4479	$171.45	$171.45	$171.40
Purchase #6	$151.85	13.560%	$172.4409	$172.44	$172.45	$172.40
Purchase #7	$91.50	11.387%	$101.9191	$101.92	$101.90	$101.90
7 purchase totals =	$745.63		$811.3132	$811.31	$811.30	$811.20