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	$229.60	4.586%	$240.1295	$240.13	$240.15	$240.10
Purchase #2	$190.60	3.119%	$196.5448	$196.54	$196.55	$196.50
Purchase #3	$234.81	13.368%	$266.1994	$266.20	$266.20	$266.20
Purchase #4	$234.89	7.191%	$251.7809	$251.78	$251.80	$251.80
Purchase #5	$233.81	6.268%	$248.4652	$248.47	$248.45	$248.50
Purchase #6	$49.81	9.623%	$54.6032	$54.60	$54.60	$54.60
Purchase #7	$213.78	8.810%	$232.614	$232.61	$232.60	$232.60
7 purchase totals =	$1,387.30		$1,490.3370	$1,490.33	$1,490.35	$1,490.30