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	$97.54	7.767%	$105.1159	$105.12	$105.10	$105.10
Purchase #2	$175.75	5.464%	$185.353	$185.35	$185.35	$185.40
Purchase #3	$217.40	9.351%	$237.7291	$237.73	$237.75	$237.70
Purchase #4	$178.63	7.221%	$191.5289	$191.53	$191.55	$191.50
Purchase #5	$133.36	6.419%	$141.9204	$141.92	$141.90	$141.90
Purchase #6	$144.51	4.773%	$151.4075	$151.41	$151.40	$151.40
Purchase #7	$59.69	4.352%	$62.2877	$62.29	$62.30	$62.30
7 purchase totals =	$1,006.88		$1,075.3425	$1,075.35	$1,075.35	$1,075.30