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	$71.65	8.397%	$77.6665	$77.67	$77.65	$77.70
Purchase #2	$236.83	3.625%	$245.4151	$245.42	$245.40	$245.40
Purchase #3	$148.94	13.326%	$168.7877	$168.79	$168.80	$168.80
Purchase #4	$15.36	3.113%	$15.8382	$15.84	$15.85	$15.80
Purchase #5	$72.91	13.640%	$82.8549	$82.85	$82.85	$82.90
Purchase #6	$198.65	9.498%	$217.5178	$217.52	$217.50	$217.50
Purchase #7	$82.61	5.388%	$87.061	$87.06	$87.05	$87.10
7 purchase totals =	$826.95		$895.1412	$895.15	$895.10	$895.20