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	$158.69	13.326%	$179.837	$179.84	$179.85	$179.80
Purchase #2	$195.82	13.661%	$222.571	$222.57	$222.55	$222.60
Purchase #3	$23.58	12.364%	$26.4954	$26.50	$26.50	$26.50
Purchase #4	$57.55	3.309%	$59.4543	$59.45	$59.45	$59.50
Purchase #5	$209.36	11.851%	$234.1713	$234.17	$234.15	$234.20
Purchase #6	$150.38	6.387%	$159.9848	$159.98	$160.00	$160.00
Purchase #7	$131.42	5.615%	$138.7992	$138.80	$138.80	$138.80
7 purchase totals =	$926.80		$1,021.3130	$1,021.31	$1,021.30	$1,021.40