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	$109.60	8.167%	$118.551	$118.55	$118.55	$118.60
Purchase #2	$50.96	6.106%	$54.0716	$54.07	$54.05	$54.10
Purchase #3	$156.28	3.349%	$161.5138	$161.51	$161.50	$161.50
Purchase #4	$142.35	3.405%	$147.197	$147.20	$147.20	$147.20
Purchase #5	$148.61	9.621%	$162.9078	$162.91	$162.90	$162.90
Purchase #6	$233.77	9.377%	$255.6906	$255.69	$255.70	$255.70
Purchase #7	$104.38	5.132%	$109.7368	$109.74	$109.75	$109.70
7 purchase totals =	$945.95		$1,009.6686	$1,009.67	$1,009.65	$1,009.70