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	$233.89	13.319%	$265.0418	$265.04	$265.05	$265.00
Purchase #2	$94.80	4.537%	$99.1011	$99.10	$99.10	$99.10
Purchase #3	$169.86	7.819%	$183.1414	$183.14	$183.15	$183.10
Purchase #4	$160.36	11.795%	$179.2745	$179.27	$179.25	$179.30
Purchase #5	$39.49	13.834%	$44.953	$44.95	$44.95	$45.00
Purchase #6	$103.52	4.511%	$108.1898	$108.19	$108.20	$108.20
Purchase #7	$109.69	13.584%	$124.5903	$124.59	$124.60	$124.60
7 purchase totals =	$911.61		$1,004.2919	$1,004.28	$1,004.30	$1,004.30