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	$208.32	5.415%	$219.6005	$219.60	$219.60	$219.60
Purchase #2	$72.34	11.534%	$80.6837	$80.68	$80.70	$80.70
Purchase #3	$42.67	3.838%	$44.3077	$44.31	$44.30	$44.30
Purchase #4	$17.25	9.579%	$18.9024	$18.90	$18.90	$18.90
Purchase #5	$17.33	6.753%	$18.5003	$18.50	$18.50	$18.50
Purchase #6	$208.70	12.745%	$235.2988	$235.30	$235.30	$235.30
Purchase #7	$54.95	8.768%	$59.768	$59.77	$59.75	$59.80
7 purchase totals =	$621.56		$677.0614	$677.06	$677.05	$677.10