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	$149.29	12.570%	$168.0558	$168.06	$168.05	$168.10
Purchase #2	$147.45	8.555%	$160.0643	$160.06	$160.05	$160.10
Purchase #3	$190.27	3.345%	$196.6345	$196.63	$196.65	$196.60
Purchase #4	$233.49	3.103%	$240.7352	$240.74	$240.75	$240.70
Purchase #5	$13.66	6.701%	$14.5754	$14.58	$14.60	$14.60
Purchase #6	$28.53	7.218%	$30.5893	$30.59	$30.60	$30.60
Purchase #7	$234.66	8.846%	$255.418	$255.42	$255.40	$255.40
7 purchase totals =	$997.35		$1,066.0725	$1,066.08	$1,066.10	$1,066.10