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	$42.63	10.286%	$47.0149	$47.01	$47.00	$47.00
Purchase #2	$115.70	11.614%	$129.1374	$129.14	$129.15	$129.10
Purchase #3	$206.89	7.166%	$221.7157	$221.72	$221.70	$221.70
Purchase #4	$216.42	7.250%	$232.1105	$232.11	$232.10	$232.10
Purchase #5	$204.83	5.433%	$215.9584	$215.96	$215.95	$216.00
Purchase #6	$71.50	10.327%	$78.8838	$78.88	$78.90	$78.90
Purchase #7	$196.75	10.325%	$217.0644	$217.06	$217.05	$217.10
7 purchase totals =	$1,054.72		$1,141.8851	$1,141.88	$1,141.85	$1,141.90