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	$31.58	5.356%	$33.2714	$33.27	$33.25	$33.30
Purchase #2	$198.88	12.469%	$223.6783	$223.68	$223.70	$223.70
Purchase #3	$51.52	3.770%	$53.4623	$53.46	$53.45	$53.50
Purchase #4	$38.30	13.371%	$43.4211	$43.42	$43.40	$43.40
Purchase #5	$247.40	11.442%	$275.7075	$275.71	$275.70	$275.70
Purchase #6	$195.52	11.868%	$218.7243	$218.72	$218.70	$218.70
Purchase #7	$117.57	6.398%	$125.0921	$125.09	$125.10	$125.10
7 purchase totals =	$880.77		$973.3570	$973.35	$973.30	$973.40