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	$67.25	4.219%	$70.0873	$70.09	$70.10	$70.10
Purchase #2	$117.42	8.442%	$127.3326	$127.33	$127.35	$127.30
Purchase #3	$95.95	8.832%	$104.4243	$104.42	$104.40	$104.40
Purchase #4	$99.46	9.680%	$109.0877	$109.09	$109.10	$109.10
Purchase #5	$21.37	13.648%	$24.2866	$24.29	$24.30	$24.30
Purchase #6	$47.86	7.650%	$51.5213	$51.52	$51.50	$51.50
Purchase #7	$232.79	6.612%	$248.1821	$248.18	$248.20	$248.20
7 purchase totals =	$682.10		$734.9219	$734.92	$734.95	$734.90