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	$51.85	4.215%	$54.0355	$54.04	$54.05	$54.00
Purchase #2	$218.52	9.474%	$239.2226	$239.22	$239.20	$239.20
Purchase #3	$23.93	12.362%	$26.8882	$26.89	$26.90	$26.90
Purchase #4	$123.93	7.177%	$132.8245	$132.82	$132.80	$132.80
Purchase #5	$94.50	11.788%	$105.6397	$105.64	$105.65	$105.60
Purchase #6	$179.62	3.721%	$186.3037	$186.30	$186.30	$186.30
Purchase #7	$243.51	12.574%	$274.1289	$274.13	$274.15	$274.10
7 purchase totals =	$935.86		$1,019.0431	$1,019.04	$1,019.05	$1,018.90