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	$12.96	8.716%	$14.0896	$14.09	$14.10	$14.10
Purchase #2	$152.82	3.651%	$158.3995	$158.40	$158.40	$158.40
Purchase #3	$223.91	8.139%	$242.134	$242.13	$242.15	$242.10
Purchase #4	$147.89	5.524%	$156.0594	$156.06	$156.05	$156.10
Purchase #5	$59.71	9.792%	$65.5568	$65.56	$65.55	$65.60
Purchase #6	$243.25	10.224%	$268.1199	$268.12	$268.10	$268.10
Purchase #7	$98.69	9.567%	$108.1317	$108.13	$108.15	$108.10
7 purchase totals =	$939.23		$1,012.4909	$1,012.49	$1,012.50	$1,012.50