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	$113.41	13.163%	$128.3382	$128.34	$128.35	$128.30
Purchase #2	$138.49	12.374%	$155.6268	$155.63	$155.65	$155.60
Purchase #3	$82.65	13.476%	$93.7879	$93.79	$93.80	$93.80
Purchase #4	$53.47	7.582%	$57.5241	$57.52	$57.50	$57.50
Purchase #5	$218.42	6.726%	$233.1109	$233.11	$233.10	$233.10
Purchase #6	$154.57	6.486%	$164.5954	$164.60	$164.60	$164.60
Purchase #7	$202.88	10.276%	$223.7279	$223.73	$223.75	$223.70
7 purchase totals =	$963.89		$1,056.7112	$1,056.72	$1,056.75	$1,056.60