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	$148.65	6.483%	$158.287	$158.29	$158.30	$158.30
Purchase #2	$128.50	4.867%	$134.7541	$134.75	$134.75	$134.80
Purchase #3	$81.56	11.574%	$90.9998	$91.00	$91.00	$91.00
Purchase #4	$89.55	13.555%	$101.6885	$101.69	$101.70	$101.70
Purchase #5	$92.33	9.293%	$100.9102	$100.91	$100.90	$100.90
Purchase #6	$34.92	9.778%	$38.3345	$38.33	$38.35	$38.30
Purchase #7	$91.51	9.502%	$100.2053	$100.21	$100.20	$100.20
7 purchase totals =	$667.02		$725.1794	$725.18	$725.20	$725.20