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	$208.98	10.166%	$230.2249	$230.22	$230.20	$230.20
Purchase #2	$108.77	13.214%	$123.1429	$123.14	$123.15	$123.10
Purchase #3	$190.78	11.567%	$212.8475	$212.85	$212.85	$212.80
Purchase #4	$168.36	4.228%	$175.4783	$175.48	$175.50	$175.50
Purchase #5	$89.36	11.735%	$99.8464	$99.85	$99.85	$99.80
Purchase #6	$219.59	3.455%	$227.1768	$227.18	$227.20	$227.20
Purchase #7	$176.85	3.430%	$182.916	$182.92	$182.90	$182.90
7 purchase totals =	$1,162.69		$1,251.6328	$1,251.64	$1,251.65	$1,251.50