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	$207.37	4.301%	$216.289	$216.29	$216.30	$216.30
Purchase #2	$39.73	4.648%	$41.5767	$41.58	$41.60	$41.60
Purchase #3	$117.30	8.446%	$127.2072	$127.21	$127.20	$127.20
Purchase #4	$115.45	10.722%	$127.8285	$127.83	$127.85	$127.80
Purchase #5	$177.49	13.732%	$201.8629	$201.86	$201.85	$201.90
Purchase #6	$243.95	12.830%	$275.2488	$275.25	$275.25	$275.20
Purchase #7	$94.40	6.343%	$100.3878	$100.39	$100.40	$100.40
7 purchase totals =	$995.69		$1,090.4009	$1,090.41	$1,090.45	$1,090.40