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	$189.49	6.780%	$202.3374	$202.34	$202.35	$202.30
Purchase #2	$159.57	3.561%	$165.2523	$165.25	$165.25	$165.30
Purchase #3	$55.46	3.815%	$57.5758	$57.58	$57.60	$57.60
Purchase #4	$14.74	4.147%	$15.3513	$15.35	$15.35	$15.40
Purchase #5	$43.88	5.763%	$46.4088	$46.41	$46.40	$46.40
Purchase #6	$37.41	13.430%	$42.4342	$42.43	$42.45	$42.40
Purchase #7	$53.58	10.796%	$59.3645	$59.36	$59.35	$59.40
7 purchase totals =	$554.13		$588.7243	$588.72	$588.75	$588.80