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	$65.73	11.217%	$73.1029	$73.10	$73.10	$73.10
Purchase #2	$151.71	4.455%	$158.4687	$158.47	$158.45	$158.50
Purchase #3	$12.56	11.661%	$14.0246	$14.02	$14.00	$14.00
Purchase #4	$116.56	6.224%	$123.8147	$123.81	$123.80	$123.80
Purchase #5	$110.87	7.728%	$119.438	$119.44	$119.45	$119.40
Purchase #6	$141.83	7.773%	$152.8544	$152.85	$152.85	$152.90
Purchase #7	$5.81	7.616%	$6.2525	$6.25	$6.25	$6.30
7 purchase totals =	$605.07		$647.9558	$647.94	$647.90	$648.00