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	$129.62	9.797%	$142.3189	$142.32	$142.30	$142.30
Purchase #2	$199.93	12.163%	$224.2475	$224.25	$224.25	$224.20
Purchase #3	$18.73	10.213%	$20.6429	$20.64	$20.65	$20.60
Purchase #4	$142.62	4.817%	$149.49	$149.49	$149.50	$149.50
Purchase #5	$239.64	12.769%	$270.2396	$270.24	$270.25	$270.20
Purchase #6	$97.89	12.294%	$109.9246	$109.92	$109.90	$109.90
Purchase #7	$52.86	13.320%	$59.901	$59.90	$59.90	$59.90
7 purchase totals =	$881.29		$976.7645	$976.76	$976.75	$976.60