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	$39.92	7.681%	$42.9863	$42.99	$43.00	$43.00
Purchase #2	$118.75	7.428%	$127.5708	$127.57	$127.55	$127.60
Purchase #3	$189.29	11.201%	$210.4924	$210.49	$210.50	$210.50
Purchase #4	$167.95	13.521%	$190.6585	$190.66	$190.65	$190.70
Purchase #5	$82.52	7.835%	$88.9854	$88.99	$89.00	$89.00
Purchase #6	$120.33	6.253%	$127.8542	$127.85	$127.85	$127.90
Purchase #7	$147.26	11.544%	$164.2597	$164.26	$164.25	$164.30
7 purchase totals =	$866.02		$952.8073	$952.81	$952.80	$953.00