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	$222.96	13.649%	$253.3918	$253.39	$253.40	$253.40
Purchase #2	$114.69	10.826%	$127.1063	$127.11	$127.10	$127.10
Purchase #3	$68.81	13.730%	$78.2576	$78.26	$78.25	$78.30
Purchase #4	$196.98	10.696%	$218.049	$218.05	$218.05	$218.00
Purchase #5	$112.42	6.339%	$119.5463	$119.55	$119.55	$119.50
Purchase #6	$47.46	4.153%	$49.431	$49.43	$49.45	$49.40
Purchase #7	$167.87	8.327%	$181.8485	$181.85	$181.85	$181.80
7 purchase totals =	$931.19		$1,027.6305	$1,027.64	$1,027.65	$1,027.50