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	$12.89	10.784%	$14.2801	$14.28	$14.30	$14.30
Purchase #2	$202.50	6.606%	$215.8772	$215.88	$215.90	$215.90
Purchase #3	$158.49	5.803%	$167.6872	$167.69	$167.70	$167.70
Purchase #4	$74.82	4.324%	$78.0552	$78.06	$78.05	$78.10
Purchase #5	$246.87	7.244%	$264.7533	$264.75	$264.75	$264.80
Purchase #6	$122.48	5.280%	$128.9469	$128.95	$128.95	$128.90
Purchase #7	$122.77	7.675%	$132.1926	$132.19	$132.20	$132.20
7 purchase totals =	$940.82		$1,001.7925	$1,001.80	$1,001.85	$1,001.90