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	$11.52	4.525%	$12.0413	$12.04	$12.05	$12.00
Purchase #2	$91.35	7.448%	$98.1537	$98.15	$98.15	$98.20
Purchase #3	$199.94	4.434%	$208.8053	$208.81	$208.80	$208.80
Purchase #4	$79.49	4.112%	$82.7586	$82.76	$82.75	$82.80
Purchase #5	$40.68	10.761%	$45.0576	$45.06	$45.05	$45.10
Purchase #6	$100.90	4.793%	$105.7361	$105.74	$105.75	$105.70
Purchase #7	$152.69	9.860%	$167.7452	$167.75	$167.75	$167.70
7 purchase totals =	$676.57		$720.2978	$720.31	$720.30	$720.30