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	$125.36	3.486%	$129.73	$129.73	$129.75	$129.70
Purchase #2	$86.45	13.300%	$97.9479	$97.95	$97.95	$97.90
Purchase #3	$65.39	9.417%	$71.5478	$71.55	$71.55	$71.50
Purchase #4	$25.68	6.871%	$27.4445	$27.44	$27.45	$27.40
Purchase #5	$134.30	12.452%	$151.023	$151.02	$151.00	$151.00
Purchase #6	$52.39	13.581%	$59.5051	$59.51	$59.50	$59.50
Purchase #7	$228.80	11.380%	$254.8374	$254.84	$254.85	$254.80
7 purchase totals =	$718.37		$792.0357	$792.04	$792.05	$791.80