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	$12.26	10.625%	$13.5626	$13.56	$13.55	$13.60
Purchase #2	$215.76	5.806%	$228.287	$228.29	$228.30	$228.30
Purchase #3	$164.59	6.430%	$175.1731	$175.17	$175.15	$175.20
Purchase #4	$109.97	8.711%	$119.5495	$119.55	$119.55	$119.50
Purchase #5	$187.85	4.728%	$196.7315	$196.73	$196.75	$196.70
Purchase #6	$238.26	13.551%	$270.5466	$270.55	$270.55	$270.50
Purchase #7	$153.88	7.717%	$165.7549	$165.75	$165.75	$165.80
7 purchase totals =	$1,082.57		$1,169.6052	$1,169.60	$1,169.60	$1,169.60