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	$139.92	7.442%	$150.3328	$150.33	$150.35	$150.30
Purchase #2	$100.76	11.529%	$112.3766	$112.38	$112.40	$112.40
Purchase #3	$36.40	6.640%	$38.817	$38.82	$38.80	$38.80
Purchase #4	$52.68	12.260%	$59.1386	$59.14	$59.15	$59.10
Purchase #5	$11.32	11.640%	$12.6376	$12.64	$12.65	$12.60
Purchase #6	$14.86	9.600%	$16.2866	$16.29	$16.30	$16.30
Purchase #7	$210.37	5.524%	$221.9908	$221.99	$222.00	$222.00
7 purchase totals =	$566.31		$611.5800	$611.59	$611.65	$611.50