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	$118.85	7.646%	$127.9373	$127.94	$127.95	$127.90
Purchase #2	$226.89	9.185%	$247.7298	$247.73	$247.75	$247.70
Purchase #3	$151.32	13.184%	$171.27	$171.27	$171.25	$171.30
Purchase #4	$229.65	3.105%	$236.7806	$236.78	$236.80	$236.80
Purchase #5	$215.76	5.701%	$228.0605	$228.06	$228.05	$228.10
Purchase #6	$9.96	8.374%	$10.7941	$10.79	$10.80	$10.80
Purchase #7	$35.26	7.323%	$37.8421	$37.84	$37.85	$37.80
7 purchase totals =	$987.69		$1,060.4144	$1,060.41	$1,060.45	$1,060.40