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	$180.85	7.610%	$194.6127	$194.61	$194.60	$194.60
Purchase #2	$7.35	13.261%	$8.3247	$8.32	$8.30	$8.30
Purchase #3	$7.49	3.567%	$7.7572	$7.76	$7.75	$7.80
Purchase #4	$118.25	10.749%	$130.9607	$130.96	$130.95	$131.00
Purchase #5	$39.54	13.155%	$44.7415	$44.74	$44.75	$44.70
Purchase #6	$20.55	4.120%	$21.3967	$21.40	$21.40	$21.40
Purchase #7	$174.56	12.334%	$196.0902	$196.09	$196.10	$196.10
7 purchase totals =	$548.59		$603.8837	$603.88	$603.85	$603.90