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	$34.41	5.800%	$36.4058	$36.41	$36.40	$36.40
Purchase #2	$223.41	5.506%	$235.711	$235.71	$235.70	$235.70
Purchase #3	$232.25	8.153%	$251.1853	$251.19	$251.20	$251.20
Purchase #4	$99.39	4.277%	$103.6409	$103.64	$103.65	$103.60
Purchase #5	$198.76	11.759%	$222.1322	$222.13	$222.15	$222.10
Purchase #6	$30.34	4.185%	$31.6097	$31.61	$31.60	$31.60
Purchase #7	$179.51	9.235%	$196.0877	$196.09	$196.10	$196.10
7 purchase totals =	$998.07		$1,076.7726	$1,076.78	$1,076.80	$1,076.70