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	$205.77	6.687%	$219.5298	$219.53	$219.55	$219.50
Purchase #2	$211.89	12.598%	$238.5839	$238.58	$238.60	$238.60
Purchase #3	$197.52	7.521%	$212.3755	$212.38	$212.40	$212.40
Purchase #4	$9.41	4.340%	$9.8184	$9.82	$9.80	$9.80
Purchase #5	$82.91	9.578%	$90.8511	$90.85	$90.85	$90.90
Purchase #6	$68.57	7.218%	$73.5194	$73.52	$73.50	$73.50
Purchase #7	$195.73	13.874%	$222.8856	$222.89	$222.90	$222.90
7 purchase totals =	$971.80		$1,067.5637	$1,067.57	$1,067.60	$1,067.60