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	$83.87	3.166%	$86.5253	$86.53	$86.55	$86.50
Purchase #2	$201.69	4.666%	$211.1009	$211.10	$211.10	$211.10
Purchase #3	$179.41	6.511%	$191.0914	$191.09	$191.10	$191.10
Purchase #4	$140.44	11.176%	$156.1356	$156.14	$156.15	$156.10
Purchase #5	$238.54	9.179%	$260.4356	$260.44	$260.45	$260.40
Purchase #6	$116.61	7.493%	$125.3476	$125.35	$125.35	$125.30
Purchase #7	$28.91	7.570%	$31.0985	$31.10	$31.10	$31.10
7 purchase totals =	$989.47		$1,061.7349	$1,061.75	$1,061.80	$1,061.60