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	$97.80	5.565%	$103.2426	$103.24	$103.25	$103.20
Purchase #2	$142.34	12.654%	$160.3517	$160.35	$160.35	$160.40
Purchase #3	$171.88	5.181%	$180.7851	$180.79	$180.80	$180.80
Purchase #4	$204.61	5.277%	$215.4073	$215.41	$215.40	$215.40
Purchase #5	$180.98	7.412%	$194.3942	$194.39	$194.40	$194.40
Purchase #6	$59.29	4.861%	$62.1721	$62.17	$62.15	$62.20
Purchase #7	$128.47	6.837%	$137.2535	$137.25	$137.25	$137.30
7 purchase totals =	$985.37		$1,053.6065	$1,053.60	$1,053.60	$1,053.70