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	$187.83	4.523%	$196.3256	$196.33	$196.35	$196.30
Purchase #2	$88.98	3.447%	$92.0471	$92.05	$92.05	$92.00
Purchase #3	$236.48	12.512%	$266.0684	$266.07	$266.05	$266.10
Purchase #4	$162.51	9.565%	$178.0541	$178.05	$178.05	$178.10
Purchase #5	$130.78	4.517%	$136.6873	$136.69	$136.70	$136.70
Purchase #6	$105.49	12.349%	$118.517	$118.52	$118.50	$118.50
Purchase #7	$29.60	7.131%	$31.7108	$31.71	$31.70	$31.70
7 purchase totals =	$941.67		$1,019.4103	$1,019.42	$1,019.40	$1,019.40