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	$157.84	8.856%	$171.8183	$171.82	$171.80	$171.80
Purchase #2	$54.62	11.861%	$61.0985	$61.10	$61.10	$61.10
Purchase #3	$125.82	13.550%	$142.8686	$142.87	$142.85	$142.90
Purchase #4	$48.90	3.319%	$50.523	$50.52	$50.50	$50.50
Purchase #5	$131.90	13.769%	$150.0613	$150.06	$150.05	$150.10
Purchase #6	$242.94	13.274%	$275.1879	$275.19	$275.20	$275.20
Purchase #7	$164.95	5.872%	$174.6359	$174.64	$174.65	$174.60
7 purchase totals =	$926.97		$1,026.1935	$1,026.20	$1,026.15	$1,026.20