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	$115.91	10.225%	$127.7618	$127.76	$127.75	$127.80
Purchase #2	$39.47	8.699%	$42.9035	$42.90	$42.90	$42.90
Purchase #3	$190.57	3.270%	$196.8016	$196.80	$196.80	$196.80
Purchase #4	$225.85	10.160%	$248.7964	$248.80	$248.80	$248.80
Purchase #5	$35.64	4.228%	$37.1469	$37.15	$37.15	$37.10
Purchase #6	$16.80	8.140%	$18.1675	$18.17	$18.15	$18.20
Purchase #7	$225.54	13.191%	$255.291	$255.29	$255.30	$255.30
7 purchase totals =	$849.78		$926.8687	$926.87	$926.85	$926.90