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	$104.65	11.848%	$117.0489	$117.05	$117.05	$117.00
Purchase #2	$77.78	6.124%	$82.5432	$82.54	$82.55	$82.50
Purchase #3	$77.67	11.551%	$86.6417	$86.64	$86.65	$86.60
Purchase #4	$243.82	6.138%	$258.7857	$258.79	$258.80	$258.80
Purchase #5	$233.73	7.458%	$251.1616	$251.16	$251.15	$251.20
Purchase #6	$166.41	12.577%	$187.3394	$187.34	$187.35	$187.30
Purchase #7	$69.38	4.356%	$72.4022	$72.40	$72.40	$72.40
7 purchase totals =	$973.44		$1,055.9227	$1,055.92	$1,055.95	$1,055.80