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	$72.33	13.455%	$82.062	$82.06	$82.05	$82.10
Purchase #2	$242.33	3.541%	$250.9109	$250.91	$250.90	$250.90
Purchase #3	$95.44	8.142%	$103.2107	$103.21	$103.20	$103.20
Purchase #4	$225.55	12.337%	$253.3761	$253.38	$253.40	$253.40
Purchase #5	$161.26	11.330%	$179.5308	$179.53	$179.55	$179.50
Purchase #6	$243.56	11.540%	$271.6668	$271.67	$271.65	$271.70
Purchase #7	$175.33	8.653%	$190.5013	$190.50	$190.50	$190.50
7 purchase totals =	$1,215.80		$1,331.2586	$1,331.26	$1,331.25	$1,331.30