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	$178.91	3.771%	$185.6567	$185.66	$185.65	$185.70
Purchase #2	$66.25	6.498%	$70.5549	$70.55	$70.55	$70.60
Purchase #3	$48.90	10.102%	$53.8399	$53.84	$53.85	$53.80
Purchase #4	$55.84	11.512%	$62.2683	$62.27	$62.25	$62.30
Purchase #5	$51.27	6.269%	$54.4841	$54.48	$54.50	$54.50
Purchase #6	$13.71	6.435%	$14.5922	$14.59	$14.60	$14.60
Purchase #7	$21.91	11.287%	$24.383	$24.38	$24.40	$24.40
7 purchase totals =	$436.79		$465.7791	$465.77	$465.80	$465.90