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	$241.33	3.696%	$250.2496	$250.25	$250.25	$250.20
Purchase #2	$127.59	4.529%	$133.3686	$133.37	$133.35	$133.40
Purchase #3	$127.86	10.721%	$141.5679	$141.57	$141.55	$141.60
Purchase #4	$15.98	6.497%	$17.0182	$17.02	$17.00	$17.00
Purchase #5	$135.28	5.271%	$142.4106	$142.41	$142.40	$142.40
Purchase #6	$75.97	5.471%	$80.1263	$80.13	$80.15	$80.10
Purchase #7	$52.50	13.245%	$59.4536	$59.45	$59.45	$59.50
7 purchase totals =	$776.51		$824.1948	$824.20	$824.15	$824.20