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	$222.81	5.573%	$235.2272	$235.23	$235.25	$235.20
Purchase #2	$55.35	8.209%	$59.8937	$59.89	$59.90	$59.90
Purchase #3	$154.99	8.655%	$168.4044	$168.40	$168.40	$168.40
Purchase #4	$173.60	4.439%	$181.3061	$181.31	$181.30	$181.30
Purchase #5	$48.37	10.716%	$53.5533	$53.55	$53.55	$53.60
Purchase #6	$195.63	4.726%	$204.8755	$204.88	$204.90	$204.90
Purchase #7	$149.83	7.643%	$161.2815	$161.28	$161.30	$161.30
7 purchase totals =	$1,000.58		$1,064.5417	$1,064.54	$1,064.60	$1,064.60