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	$88.92	4.437%	$92.8654	$92.87	$92.85	$92.90
Purchase #2	$18.50	6.697%	$19.7389	$19.74	$19.75	$19.70
Purchase #3	$160.78	11.577%	$179.3935	$179.39	$179.40	$179.40
Purchase #4	$119.46	12.585%	$134.494	$134.49	$134.50	$134.50
Purchase #5	$53.38	10.759%	$59.1232	$59.12	$59.10	$59.10
Purchase #6	$247.88	4.174%	$258.2265	$258.23	$258.25	$258.20
Purchase #7	$43.25	4.496%	$45.1945	$45.19	$45.20	$45.20
7 purchase totals =	$732.17		$789.0360	$789.03	$789.05	$789.00