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	$105.50	5.453%	$111.2529	$111.25	$111.25	$111.30
Purchase #2	$63.78	3.312%	$65.8924	$65.89	$65.90	$65.90
Purchase #3	$180.91	7.159%	$193.8613	$193.86	$193.85	$193.90
Purchase #4	$227.60	7.153%	$243.8802	$243.88	$243.90	$243.90
Purchase #5	$16.25	10.170%	$17.9026	$17.90	$17.90	$17.90
Purchase #6	$136.88	3.801%	$142.0828	$142.08	$142.10	$142.10
Purchase #7	$244.73	9.802%	$268.7184	$268.72	$268.70	$268.70
7 purchase totals =	$975.65		$1,043.5906	$1,043.58	$1,043.60	$1,043.70