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	$223.66	4.326%	$233.3355	$233.34	$233.35	$233.30
Purchase #2	$137.49	3.731%	$142.6198	$142.62	$142.60	$142.60
Purchase #3	$125.61	13.258%	$142.2634	$142.26	$142.25	$142.30
Purchase #4	$165.57	8.671%	$179.9266	$179.93	$179.95	$179.90
Purchase #5	$179.85	5.200%	$189.2022	$189.20	$189.20	$189.20
Purchase #6	$91.75	9.494%	$100.4607	$100.46	$100.45	$100.50
Purchase #7	$39.91	11.206%	$44.3823	$44.38	$44.40	$44.40
7 purchase totals =	$963.84		$1,032.1905	$1,032.19	$1,032.20	$1,032.20