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	$210.96	3.514%	$218.3731	$218.37	$218.35	$218.40
Purchase #2	$55.28	3.603%	$57.2717	$57.27	$57.25	$57.30
Purchase #3	$141.36	6.275%	$150.2303	$150.23	$150.25	$150.20
Purchase #4	$133.50	6.789%	$142.5633	$142.56	$142.55	$142.60
Purchase #5	$105.41	7.221%	$113.0217	$113.02	$113.00	$113.00
Purchase #6	$148.40	3.349%	$153.3699	$153.37	$153.35	$153.40
Purchase #7	$14.88	10.819%	$16.4899	$16.49	$16.50	$16.50
7 purchase totals =	$809.79		$851.3199	$851.31	$851.25	$851.40