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	$119.60	6.399%	$127.2532	$127.25	$127.25	$127.30
Purchase #2	$18.46	3.257%	$19.0612	$19.06	$19.05	$19.10
Purchase #3	$58.45	10.124%	$64.3675	$64.37	$64.35	$64.40
Purchase #4	$99.26	12.567%	$111.734	$111.73	$111.75	$111.70
Purchase #5	$30.88	13.577%	$35.0726	$35.07	$35.05	$35.10
Purchase #6	$73.92	8.842%	$80.456	$80.46	$80.45	$80.50
Purchase #7	$80.63	13.598%	$91.5941	$91.59	$91.60	$91.60
7 purchase totals =	$481.20		$529.5386	$529.53	$529.50	$529.70