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	$244.80	9.567%	$268.22	$268.22	$268.20	$268.20
Purchase #2	$73.55	8.221%	$79.5965	$79.60	$79.60	$79.60
Purchase #3	$156.44	6.275%	$166.2566	$166.26	$166.25	$166.30
Purchase #4	$131.32	10.418%	$145.0009	$145.00	$145.00	$145.00
Purchase #5	$120.76	5.663%	$127.5986	$127.60	$127.60	$127.60
Purchase #6	$166.35	11.675%	$185.7714	$185.77	$185.75	$185.80
Purchase #7	$91.31	8.441%	$99.0175	$99.02	$99.00	$99.00
7 purchase totals =	$984.53		$1,071.4615	$1,071.47	$1,071.40	$1,071.50