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	$18.33	5.256%	$19.2934	$19.29	$19.30	$19.30
Purchase #2	$86.99	6.421%	$92.5756	$92.58	$92.60	$92.60
Purchase #3	$53.30	10.808%	$59.0607	$59.06	$59.05	$59.10
Purchase #4	$230.89	5.172%	$242.8316	$242.83	$242.85	$242.80
Purchase #5	$84.47	4.586%	$88.3438	$88.34	$88.35	$88.30
Purchase #6	$39.89	5.594%	$42.1214	$42.12	$42.10	$42.10
Purchase #7	$206.78	6.808%	$220.8576	$220.86	$220.85	$220.90
7 purchase totals =	$720.65		$765.0841	$765.08	$765.10	$765.10