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	$14.91	7.195%	$15.9828	$15.98	$16.00	$16.00
Purchase #2	$64.96	5.130%	$68.2924	$68.29	$68.30	$68.30
Purchase #3	$142.48	8.165%	$154.1135	$154.11	$154.10	$154.10
Purchase #4	$38.86	8.471%	$42.1518	$42.15	$42.15	$42.20
Purchase #5	$43.79	3.603%	$45.3678	$45.37	$45.35	$45.40
Purchase #6	$54.85	7.623%	$59.0312	$59.03	$59.05	$59.00
Purchase #7	$90.94	13.795%	$103.4852	$103.49	$103.50	$103.50
7 purchase totals =	$450.79		$488.4247	$488.42	$488.45	$488.50