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	$94.86	4.652%	$99.2729	$99.27	$99.25	$99.30
Purchase #2	$244.59	3.624%	$253.4539	$253.45	$253.45	$253.50
Purchase #3	$55.38	7.131%	$59.3291	$59.33	$59.35	$59.30
Purchase #4	$88.68	5.469%	$93.5299	$93.53	$93.55	$93.50
Purchase #5	$220.29	4.689%	$230.6194	$230.62	$230.60	$230.60
Purchase #6	$207.82	3.704%	$215.5177	$215.52	$215.50	$215.50
Purchase #7	$131.81	10.742%	$145.969	$145.97	$145.95	$146.00
7 purchase totals =	$1,043.43		$1,097.6919	$1,097.69	$1,097.65	$1,097.70