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	$215.41	5.110%	$226.4175	$226.42	$226.40	$226.40
Purchase #2	$26.40	6.155%	$28.0249	$28.02	$28.00	$28.00
Purchase #3	$78.61	13.609%	$89.308	$89.31	$89.30	$89.30
Purchase #4	$64.90	8.502%	$70.4178	$70.42	$70.40	$70.40
Purchase #5	$166.28	8.516%	$180.4404	$180.44	$180.45	$180.40
Purchase #6	$196.80	9.542%	$215.5787	$215.58	$215.60	$215.60
Purchase #7	$176.96	8.556%	$192.1007	$192.10	$192.10	$192.10
7 purchase totals =	$925.36		$1,002.2880	$1,002.29	$1,002.25	$1,002.20