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	$107.26	4.763%	$112.3688	$112.37	$112.35	$112.40
Purchase #2	$67.85	7.721%	$73.0887	$73.09	$73.10	$73.10
Purchase #3	$189.79	13.361%	$215.1478	$215.15	$215.15	$215.10
Purchase #4	$222.71	3.223%	$229.8879	$229.89	$229.90	$229.90
Purchase #5	$72.69	4.865%	$76.2264	$76.23	$76.25	$76.20
Purchase #6	$104.54	6.290%	$111.1156	$111.12	$111.10	$111.10
Purchase #7	$157.42	3.792%	$163.3894	$163.39	$163.40	$163.40
7 purchase totals =	$922.26		$981.2246	$981.24	$981.25	$981.20