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	$107.92	9.554%	$118.2307	$118.23	$118.25	$118.20
Purchase #2	$55.50	10.848%	$61.5206	$61.52	$61.50	$61.50
Purchase #3	$62.29	10.104%	$68.5838	$68.58	$68.60	$68.60
Purchase #4	$77.42	11.692%	$86.4719	$86.47	$86.45	$86.50
Purchase #5	$123.89	9.709%	$135.9185	$135.92	$135.90	$135.90
Purchase #6	$150.69	13.786%	$171.4641	$171.46	$171.45	$171.50
Purchase #7	$124.57	5.210%	$131.0601	$131.06	$131.05	$131.10
7 purchase totals =	$702.28		$773.2497	$773.24	$773.20	$773.30