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	$185.87	6.296%	$197.5724	$197.57	$197.55	$197.60
Purchase #2	$155.98	6.330%	$165.8535	$165.85	$165.85	$165.90
Purchase #3	$188.45	11.343%	$209.8259	$209.83	$209.85	$209.80
Purchase #4	$53.86	6.158%	$57.1767	$57.18	$57.20	$57.20
Purchase #5	$35.35	10.191%	$38.9525	$38.95	$38.95	$39.00
Purchase #6	$54.37	9.263%	$59.4063	$59.41	$59.40	$59.40
Purchase #7	$35.57	10.291%	$39.2305	$39.23	$39.25	$39.20
7 purchase totals =	$709.45		$768.0178	$768.02	$768.05	$768.10