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	$91.74	7.365%	$98.4967	$98.50	$98.50	$98.50
Purchase #2	$128.55	6.758%	$137.2374	$137.24	$137.25	$137.20
Purchase #3	$52.80	5.139%	$55.5134	$55.51	$55.50	$55.50
Purchase #4	$160.29	4.763%	$167.9246	$167.92	$167.90	$167.90
Purchase #5	$96.66	5.273%	$101.7569	$101.76	$101.75	$101.80
Purchase #6	$223.36	7.526%	$240.1701	$240.17	$240.15	$240.20
Purchase #7	$158.81	4.143%	$165.3895	$165.39	$165.40	$165.40
7 purchase totals =	$912.21		$966.4886	$966.49	$966.45	$966.50