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	$65.96	8.116%	$71.3133	$71.31	$71.30	$71.30
Purchase #2	$222.25	6.331%	$236.3206	$236.32	$236.30	$236.30
Purchase #3	$213.80	5.810%	$226.2218	$226.22	$226.20	$226.20
Purchase #4	$53.70	10.498%	$59.3374	$59.34	$59.35	$59.30
Purchase #5	$92.43	10.772%	$102.3866	$102.39	$102.40	$102.40
Purchase #6	$152.68	9.822%	$167.6762	$167.68	$167.70	$167.70
Purchase #7	$67.91	3.808%	$70.496	$70.50	$70.50	$70.50
7 purchase totals =	$868.73		$933.7519	$933.76	$933.75	$933.70