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	$192.81	10.405%	$212.8719	$212.87	$212.85	$212.90
Purchase #2	$86.76	3.632%	$89.9111	$89.91	$89.90	$89.90
Purchase #3	$111.72	10.202%	$123.1177	$123.12	$123.10	$123.10
Purchase #4	$197.48	12.566%	$222.2953	$222.30	$222.30	$222.30
Purchase #5	$21.70	12.242%	$24.3565	$24.36	$24.35	$24.40
Purchase #6	$197.94	7.600%	$212.9834	$212.98	$213.00	$213.00
Purchase #7	$108.48	9.332%	$118.6034	$118.60	$118.60	$118.60
7 purchase totals =	$916.89		$1,004.1393	$1,004.14	$1,004.10	$1,004.20