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	$214.29	4.256%	$223.4102	$223.41	$223.40	$223.40
Purchase #2	$64.50	6.266%	$68.5416	$68.54	$68.55	$68.50
Purchase #3	$216.55	3.523%	$224.1791	$224.18	$224.20	$224.20
Purchase #4	$53.72	11.488%	$59.8914	$59.89	$59.90	$59.90
Purchase #5	$212.29	4.818%	$222.5181	$222.52	$222.50	$222.50
Purchase #6	$64.47	4.302%	$67.2435	$67.24	$67.25	$67.20
Purchase #7	$211.98	5.813%	$224.3024	$224.30	$224.30	$224.30
7 purchase totals =	$1,037.80		$1,090.0863	$1,090.08	$1,090.10	$1,090.00