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	$152.87	9.424%	$167.2765	$167.28	$167.30	$167.30
Purchase #2	$154.88	4.247%	$161.4578	$161.46	$161.45	$161.50
Purchase #3	$157.59	11.779%	$176.1525	$176.15	$176.15	$176.20
Purchase #4	$129.43	5.122%	$136.0594	$136.06	$136.05	$136.10
Purchase #5	$160.61	5.678%	$169.7294	$169.73	$169.75	$169.70
Purchase #6	$103.57	7.611%	$111.4527	$111.45	$111.45	$111.50
Purchase #7	$88.72	11.699%	$99.0994	$99.10	$99.10	$99.10
7 purchase totals =	$947.67		$1,021.2277	$1,021.23	$1,021.25	$1,021.40