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	$177.34	10.588%	$196.1168	$196.12	$196.10	$196.10
Purchase #2	$243.83	10.254%	$268.8323	$268.83	$268.85	$268.80
Purchase #3	$71.53	9.671%	$78.4477	$78.45	$78.45	$78.40
Purchase #4	$199.45	7.718%	$214.8436	$214.84	$214.85	$214.80
Purchase #5	$152.69	6.812%	$163.0912	$163.09	$163.10	$163.10
Purchase #6	$136.38	10.119%	$150.1803	$150.18	$150.20	$150.20
Purchase #7	$165.60	4.396%	$172.8798	$172.88	$172.90	$172.90
7 purchase totals =	$1,146.82		$1,244.3917	$1,244.39	$1,244.45	$1,244.30