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	$238.87	6.357%	$254.055	$254.06	$254.05	$254.10
Purchase #2	$108.26	3.301%	$111.8337	$111.83	$111.85	$111.80
Purchase #3	$17.48	4.127%	$18.2014	$18.20	$18.20	$18.20
Purchase #4	$196.64	7.140%	$210.6801	$210.68	$210.70	$210.70
Purchase #5	$160.56	12.540%	$180.6942	$180.69	$180.70	$180.70
Purchase #6	$161.90	13.255%	$183.3598	$183.36	$183.35	$183.40
Purchase #7	$140.97	6.644%	$150.336	$150.34	$150.35	$150.30
7 purchase totals =	$1,024.68		$1,109.1602	$1,109.16	$1,109.20	$1,109.20