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	$77.94	10.500%	$86.1237	$86.12	$86.10	$86.10
Purchase #2	$13.36	10.258%	$14.7305	$14.73	$14.75	$14.70
Purchase #3	$101.45	7.693%	$109.2545	$109.25	$109.25	$109.30
Purchase #4	$185.58	11.669%	$207.2353	$207.24	$207.25	$207.20
Purchase #5	$193.76	11.810%	$216.6431	$216.64	$216.65	$216.60
Purchase #6	$56.60	5.858%	$59.9156	$59.92	$59.90	$59.90
Purchase #7	$116.74	13.525%	$132.5291	$132.53	$132.55	$132.50
7 purchase totals =	$745.43		$826.4318	$826.43	$826.45	$826.30