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	$101.69	13.852%	$115.7761	$115.78	$115.80	$115.80
Purchase #2	$153.72	11.815%	$171.882	$171.88	$171.90	$171.90
Purchase #3	$55.57	13.227%	$62.9202	$62.92	$62.90	$62.90
Purchase #4	$195.86	11.554%	$218.4897	$218.49	$218.50	$218.50
Purchase #5	$84.38	11.174%	$93.8086	$93.81	$93.80	$93.80
Purchase #6	$215.88	3.470%	$223.371	$223.37	$223.35	$223.40
Purchase #7	$40.63	12.519%	$45.7165	$45.72	$45.70	$45.70
7 purchase totals =	$847.73		$931.9641	$931.97	$931.95	$932.00