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	$30.52	9.335%	$33.369	$33.37	$33.35	$33.40
Purchase #2	$161.43	7.817%	$174.049	$174.05	$174.05	$174.00
Purchase #3	$90.52	6.151%	$96.0879	$96.09	$96.10	$96.10
Purchase #4	$107.40	11.630%	$119.8906	$119.89	$119.90	$119.90
Purchase #5	$44.84	3.189%	$46.2699	$46.27	$46.25	$46.30
Purchase #6	$58.33	4.194%	$60.7764	$60.78	$60.80	$60.80
Purchase #7	$58.61	5.305%	$61.7193	$61.72	$61.70	$61.70
7 purchase totals =	$551.65		$592.1621	$592.17	$592.15	$592.20