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	$56.78	7.537%	$61.0595	$61.06	$61.05	$61.10
Purchase #2	$228.91	4.374%	$238.9225	$238.92	$238.90	$238.90
Purchase #3	$78.32	6.796%	$83.6426	$83.64	$83.65	$83.60
Purchase #4	$105.77	4.828%	$110.8766	$110.88	$110.90	$110.90
Purchase #5	$225.41	13.453%	$255.7344	$255.73	$255.75	$255.70
Purchase #6	$250.30	8.391%	$271.3027	$271.30	$271.30	$271.30
Purchase #7	$171.55	3.469%	$177.5011	$177.50	$177.50	$177.50
7 purchase totals =	$1,117.04		$1,199.0394	$1,199.03	$1,199.05	$1,199.00