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	$177.95	11.670%	$198.7168	$198.72	$198.70	$198.70
Purchase #2	$149.66	4.739%	$156.7524	$156.75	$156.75	$156.80
Purchase #3	$219.83	8.476%	$238.4628	$238.46	$238.45	$238.50
Purchase #4	$28.35	13.520%	$32.1829	$32.18	$32.20	$32.20
Purchase #5	$249.50	9.783%	$273.9086	$273.91	$273.90	$273.90
Purchase #6	$49.52	4.226%	$51.6127	$51.61	$51.60	$51.60
Purchase #7	$103.66	5.364%	$109.2203	$109.22	$109.20	$109.20
7 purchase totals =	$978.47		$1,060.8565	$1,060.85	$1,060.80	$1,060.90