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	$55.42	7.531%	$59.5937	$59.59	$59.60	$59.60
Purchase #2	$226.36	5.335%	$238.4363	$238.44	$238.45	$238.40
Purchase #3	$146.62	12.348%	$164.7246	$164.72	$164.70	$164.70
Purchase #4	$205.66	11.360%	$229.023	$229.02	$229.00	$229.00
Purchase #5	$27.68	6.314%	$29.4277	$29.43	$29.45	$29.40
Purchase #6	$110.51	11.612%	$123.3424	$123.34	$123.35	$123.30
Purchase #7	$54.80	6.537%	$58.3823	$58.38	$58.40	$58.40
7 purchase totals =	$827.05		$902.9300	$902.92	$902.95	$902.80