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	$31.83	10.284%	$35.1034	$35.10	$35.10	$35.10
Purchase #2	$99.79	5.651%	$105.4291	$105.43	$105.45	$105.40
Purchase #3	$197.90	5.470%	$208.7251	$208.73	$208.75	$208.70
Purchase #4	$26.84	5.422%	$28.2953	$28.30	$28.30	$28.30
Purchase #5	$239.43	10.493%	$264.5534	$264.55	$264.55	$264.60
Purchase #6	$134.32	4.588%	$140.4826	$140.48	$140.50	$140.50
Purchase #7	$82.30	10.287%	$90.7662	$90.77	$90.75	$90.80
7 purchase totals =	$812.41		$873.3551	$873.36	$873.40	$873.40