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	$93.50	5.461%	$98.606	$98.61	$98.60	$98.60
Purchase #2	$243.97	5.809%	$258.1422	$258.14	$258.15	$258.10
Purchase #3	$179.49	11.166%	$199.5319	$199.53	$199.55	$199.50
Purchase #4	$183.42	5.118%	$192.8074	$192.81	$192.80	$192.80
Purchase #5	$68.51	4.173%	$71.3689	$71.37	$71.35	$71.40
Purchase #6	$36.82	13.607%	$41.8301	$41.83	$41.85	$41.80
Purchase #7	$248.93	12.811%	$280.8204	$280.82	$280.80	$280.80
7 purchase totals =	$1,054.64		$1,143.1069	$1,143.11	$1,143.10	$1,143.00