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	$174.67	7.832%	$188.3502	$188.35	$188.35	$188.40
Purchase #2	$140.90	13.454%	$159.8567	$159.86	$159.85	$159.90
Purchase #3	$123.28	3.739%	$127.8894	$127.89	$127.90	$127.90
Purchase #4	$95.38	5.183%	$100.3235	$100.32	$100.30	$100.30
Purchase #5	$247.82	5.357%	$261.0957	$261.10	$261.10	$261.10
Purchase #6	$180.45	7.347%	$193.7077	$193.71	$193.70	$193.70
Purchase #7	$170.78	12.529%	$192.177	$192.18	$192.20	$192.20
7 purchase totals =	$1,133.28		$1,223.4002	$1,223.41	$1,223.40	$1,223.50