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	$230.81	9.724%	$253.254	$253.25	$253.25	$253.30
Purchase #2	$250.27	9.249%	$273.4175	$273.42	$273.40	$273.40
Purchase #3	$69.40	13.413%	$78.7086	$78.71	$78.70	$78.70
Purchase #4	$190.25	13.340%	$215.6294	$215.63	$215.65	$215.60
Purchase #5	$31.76	6.745%	$33.9022	$33.90	$33.90	$33.90
Purchase #6	$168.36	7.244%	$180.556	$180.56	$180.55	$180.60
Purchase #7	$49.68	8.580%	$53.9425	$53.94	$53.95	$53.90
7 purchase totals =	$990.53		$1,089.4102	$1,089.41	$1,089.40	$1,089.40