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	$56.92	4.544%	$59.5064	$59.51	$59.50	$59.50
Purchase #2	$184.78	9.347%	$202.0514	$202.05	$202.05	$202.10
Purchase #3	$106.76	4.498%	$111.5621	$111.56	$111.55	$111.60
Purchase #4	$20.98	8.436%	$22.7499	$22.75	$22.75	$22.70
Purchase #5	$226.71	8.304%	$245.536	$245.54	$245.55	$245.50
Purchase #6	$94.41	9.104%	$103.0051	$103.01	$103.00	$103.00
Purchase #7	$39.57	7.247%	$42.4376	$42.44	$42.45	$42.40
7 purchase totals =	$730.13		$786.8485	$786.86	$786.85	$786.80