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	$98.80	6.122%	$104.8485	$104.85	$104.85	$104.80
Purchase #2	$147.27	6.861%	$157.3742	$157.37	$157.35	$157.40
Purchase #3	$99.72	11.372%	$111.0602	$111.06	$111.05	$111.10
Purchase #4	$209.56	6.370%	$222.909	$222.91	$222.90	$222.90
Purchase #5	$235.78	10.131%	$259.6669	$259.67	$259.65	$259.70
Purchase #6	$27.58	3.229%	$28.4706	$28.47	$28.45	$28.50
Purchase #7	$45.95	7.435%	$49.3664	$49.37	$49.35	$49.40
7 purchase totals =	$864.66		$933.6958	$933.70	$933.60	$933.80