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	$198.35	5.479%	$209.2176	$209.22	$209.20	$209.20
Purchase #2	$24.97	6.751%	$26.6557	$26.66	$26.65	$26.70
Purchase #3	$210.86	9.665%	$231.2396	$231.24	$231.25	$231.20
Purchase #4	$245.98	5.279%	$258.9653	$258.97	$258.95	$259.00
Purchase #5	$55.57	7.658%	$59.8256	$59.83	$59.85	$59.80
Purchase #6	$54.41	9.767%	$59.7242	$59.72	$59.70	$59.70
Purchase #7	$166.78	4.284%	$173.9249	$173.92	$173.90	$173.90
7 purchase totals =	$956.92		$1,019.5529	$1,019.56	$1,019.50	$1,019.50