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	$114.56	6.700%	$122.2355	$122.24	$122.25	$122.20
Purchase #2	$93.86	6.418%	$99.8839	$99.88	$99.90	$99.90
Purchase #3	$5.69	12.347%	$6.3925	$6.39	$6.40	$6.40
Purchase #4	$64.81	5.275%	$68.2287	$68.23	$68.25	$68.20
Purchase #5	$13.69	8.825%	$14.8981	$14.90	$14.90	$14.90
Purchase #6	$185.34	3.764%	$192.3162	$192.32	$192.30	$192.30
Purchase #7	$110.89	11.161%	$123.2664	$123.27	$123.25	$123.30
7 purchase totals =	$588.84		$627.2213	$627.23	$627.25	$627.20