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	$232.69	11.455%	$259.3446	$259.34	$259.35	$259.30
Purchase #2	$49.93	10.607%	$55.2261	$55.23	$55.25	$55.20
Purchase #3	$67.96	13.134%	$76.8859	$76.89	$76.90	$76.90
Purchase #4	$55.63	6.704%	$59.3594	$59.36	$59.35	$59.40
Purchase #5	$206.94	13.334%	$234.5334	$234.53	$234.55	$234.50
Purchase #6	$202.92	13.273%	$229.8536	$229.85	$229.85	$229.90
Purchase #7	$57.40	3.836%	$59.6019	$59.60	$59.60	$59.60
7 purchase totals =	$873.47		$974.8049	$974.80	$974.85	$974.80