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	$39.40	11.481%	$43.9235	$43.92	$43.90	$43.90
Purchase #2	$245.62	9.737%	$269.536	$269.54	$269.55	$269.50
Purchase #3	$163.58	6.599%	$174.3746	$174.37	$174.35	$174.40
Purchase #4	$68.52	5.262%	$72.1255	$72.13	$72.15	$72.10
Purchase #5	$33.52	13.144%	$37.9259	$37.93	$37.95	$37.90
Purchase #6	$204.53	9.382%	$223.719	$223.72	$223.70	$223.70
Purchase #7	$199.83	9.860%	$219.5332	$219.53	$219.55	$219.50
7 purchase totals =	$955.00		$1,041.1377	$1,041.14	$1,041.15	$1,041.00