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	$194.39	11.841%	$217.4077	$217.41	$217.40	$217.40
Purchase #2	$78.72	9.720%	$86.3716	$86.37	$86.35	$86.40
Purchase #3	$48.49	13.377%	$54.9765	$54.98	$55.00	$55.00
Purchase #4	$229.41	13.590%	$260.5868	$260.59	$260.60	$260.60
Purchase #5	$90.32	5.244%	$95.0564	$95.06	$95.05	$95.10
Purchase #6	$37.99	9.854%	$41.7335	$41.73	$41.75	$41.70
Purchase #7	$80.54	11.765%	$90.0155	$90.02	$90.00	$90.00
7 purchase totals =	$759.86		$846.1480	$846.16	$846.15	$846.20