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	$154.37	6.567%	$164.5075	$164.51	$164.50	$164.50
Purchase #2	$68.36	6.347%	$72.6988	$72.70	$72.70	$72.70
Purchase #3	$54.26	9.266%	$59.2877	$59.29	$59.30	$59.30
Purchase #4	$5.79	11.461%	$6.4536	$6.45	$6.45	$6.50
Purchase #5	$244.29	6.280%	$259.6314	$259.63	$259.65	$259.60
Purchase #6	$42.92	3.689%	$44.5033	$44.50	$44.50	$44.50
Purchase #7	$154.72	4.539%	$161.7427	$161.74	$161.75	$161.70
7 purchase totals =	$724.71		$768.8250	$768.82	$768.85	$768.80