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	$93.51	6.377%	$99.4731	$99.47	$99.45	$99.50
Purchase #2	$12.87	12.107%	$14.4282	$14.43	$14.45	$14.40
Purchase #3	$211.91	11.225%	$235.6969	$235.70	$235.70	$235.70
Purchase #4	$167.55	7.455%	$180.0409	$180.04	$180.05	$180.00
Purchase #5	$250.88	11.130%	$278.8029	$278.80	$278.80	$278.80
Purchase #6	$101.47	3.727%	$105.2518	$105.25	$105.25	$105.30
Purchase #7	$224.43	5.525%	$236.8298	$236.83	$236.85	$236.80
7 purchase totals =	$1,062.62		$1,150.5236	$1,150.52	$1,150.55	$1,150.50