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	$42.40	5.356%	$44.6709	$44.67	$44.65	$44.70
Purchase #2	$141.85	11.614%	$158.3245	$158.32	$158.30	$158.30
Purchase #3	$167.69	6.738%	$178.989	$178.99	$179.00	$179.00
Purchase #4	$41.35	4.341%	$43.145	$43.15	$43.15	$43.10
Purchase #5	$182.37	6.291%	$193.8429	$193.84	$193.85	$193.80
Purchase #6	$93.46	6.324%	$99.3704	$99.37	$99.35	$99.40
Purchase #7	$86.26	5.231%	$90.7723	$90.77	$90.75	$90.80
7 purchase totals =	$755.38		$809.1150	$809.11	$809.05	$809.10