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	$63.56	13.389%	$72.07	$72.07	$72.05	$72.10
Purchase #2	$62.59	11.214%	$69.6088	$69.61	$69.60	$69.60
Purchase #3	$150.90	8.680%	$163.9981	$164.00	$164.00	$164.00
Purchase #4	$250.89	5.280%	$264.137	$264.14	$264.15	$264.10
Purchase #5	$162.84	13.711%	$185.167	$185.17	$185.15	$185.20
Purchase #6	$58.50	3.751%	$60.6943	$60.69	$60.70	$60.70
Purchase #7	$235.35	12.840%	$265.5689	$265.57	$265.55	$265.60
7 purchase totals =	$984.63		$1,081.2441	$1,081.25	$1,081.20	$1,081.30