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	$195.52	4.781%	$204.8678	$204.87	$204.85	$204.90
Purchase #2	$228.90	5.221%	$240.8509	$240.85	$240.85	$240.90
Purchase #3	$53.45	11.468%	$59.5796	$59.58	$59.60	$59.60
Purchase #4	$232.59	4.582%	$243.2473	$243.25	$243.25	$243.20
Purchase #5	$142.95	9.622%	$156.7046	$156.70	$156.70	$156.70
Purchase #6	$102.28	10.538%	$113.0583	$113.06	$113.05	$113.10
Purchase #7	$125.49	13.635%	$142.6006	$142.60	$142.60	$142.60
7 purchase totals =	$1,081.18		$1,160.9091	$1,160.91	$1,160.90	$1,161.00