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	$202.78	13.567%	$230.2912	$230.29	$230.30	$230.30
Purchase #2	$154.55	13.345%	$175.1747	$175.17	$175.15	$175.20
Purchase #3	$43.93	5.582%	$46.3822	$46.38	$46.40	$46.40
Purchase #4	$229.72	5.727%	$242.8761	$242.88	$242.90	$242.90
Purchase #5	$103.33	10.765%	$114.4535	$114.45	$114.45	$114.50
Purchase #6	$142.47	4.256%	$148.5335	$148.53	$148.55	$148.50
Purchase #7	$196.79	12.801%	$221.9811	$221.98	$222.00	$222.00
7 purchase totals =	$1,073.57		$1,179.6923	$1,179.68	$1,179.75	$1,179.80