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	$116.81	7.430%	$125.489	$125.49	$125.50	$125.50
Purchase #2	$176.52	11.547%	$196.9028	$196.90	$196.90	$196.90
Purchase #3	$53.26	10.825%	$59.0254	$59.03	$59.05	$59.00
Purchase #4	$200.64	9.254%	$219.2072	$219.21	$219.20	$219.20
Purchase #5	$34.95	12.554%	$39.3376	$39.34	$39.35	$39.30
Purchase #6	$167.77	12.322%	$188.4426	$188.44	$188.45	$188.40
Purchase #7	$232.35	13.783%	$264.3748	$264.37	$264.35	$264.40
7 purchase totals =	$982.30		$1,092.7794	$1,092.78	$1,092.80	$1,092.70