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	$184.99	13.429%	$209.8323	$209.83	$209.85	$209.80
Purchase #2	$245.71	7.646%	$264.497	$264.50	$264.50	$264.50
Purchase #3	$154.29	5.234%	$162.3655	$162.37	$162.35	$162.40
Purchase #4	$145.61	3.114%	$150.1443	$150.14	$150.15	$150.10
Purchase #5	$159.61	6.473%	$169.9416	$169.94	$169.95	$169.90
Purchase #6	$27.86	9.808%	$30.5925	$30.59	$30.60	$30.60
Purchase #7	$181.54	8.801%	$197.5173	$197.52	$197.50	$197.50
7 purchase totals =	$1,099.61		$1,184.8905	$1,184.89	$1,184.90	$1,184.80