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	$203.44	10.515%	$224.8317	$224.83	$224.85	$224.80
Purchase #2	$27.94	12.669%	$31.4797	$31.48	$31.50	$31.50
Purchase #3	$179.83	10.494%	$198.7014	$198.70	$198.70	$198.70
Purchase #4	$160.78	6.651%	$171.4735	$171.47	$171.45	$171.50
Purchase #5	$81.98	9.857%	$90.0608	$90.06	$90.05	$90.10
Purchase #6	$81.32	9.646%	$89.1641	$89.16	$89.15	$89.20
Purchase #7	$182.62	13.482%	$207.2408	$207.24	$207.25	$207.20
7 purchase totals =	$917.91		$1,012.9520	$1,012.94	$1,012.95	$1,013.00