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	$39.37	9.268%	$43.0188	$43.02	$43.00	$43.00
Purchase #2	$229.96	10.604%	$254.345	$254.35	$254.35	$254.30
Purchase #3	$238.28	11.183%	$264.9269	$264.93	$264.95	$264.90
Purchase #4	$190.37	8.571%	$206.6866	$206.69	$206.70	$206.70
Purchase #5	$81.99	10.336%	$90.4645	$90.46	$90.45	$90.50
Purchase #6	$132.44	8.226%	$143.3345	$143.33	$143.35	$143.30
Purchase #7	$11.82	3.532%	$12.2375	$12.24	$12.25	$12.20
7 purchase totals =	$924.23		$1,015.0138	$1,015.02	$1,015.05	$1,014.90