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	$112.60	12.814%	$127.0286	$127.03	$127.05	$127.00
Purchase #2	$250.58	3.270%	$258.774	$258.77	$258.75	$258.80
Purchase #3	$31.27	4.278%	$32.6077	$32.61	$32.60	$32.60
Purchase #4	$132.98	11.780%	$148.645	$148.65	$148.65	$148.60
Purchase #5	$61.60	4.262%	$64.2254	$64.23	$64.25	$64.20
Purchase #6	$82.94	11.573%	$92.5386	$92.54	$92.55	$92.50
Purchase #7	$94.30	7.649%	$101.513	$101.51	$101.50	$101.50
7 purchase totals =	$766.27		$825.3323	$825.34	$825.35	$825.20