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	$52.68	7.616%	$56.6921	$56.69	$56.70	$56.70
Purchase #2	$80.97	11.225%	$90.0589	$90.06	$90.05	$90.10
Purchase #3	$51.96	13.649%	$59.052	$59.05	$59.05	$59.10
Purchase #4	$64.99	10.722%	$71.9582	$71.96	$71.95	$72.00
Purchase #5	$41.37	7.608%	$44.5174	$44.52	$44.50	$44.50
Purchase #6	$9.94	12.437%	$11.1762	$11.18	$11.20	$11.20
Purchase #7	$171.76	11.353%	$191.2599	$191.26	$191.25	$191.30
7 purchase totals =	$473.67		$524.7147	$524.72	$524.70	$524.90