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	$11.93	3.506%	$12.3483	$12.35	$12.35	$12.30
Purchase #2	$54.28	13.111%	$61.3967	$61.40	$61.40	$61.40
Purchase #3	$105.75	12.533%	$119.0036	$119.00	$119.00	$119.00
Purchase #4	$65.98	7.824%	$71.1423	$71.14	$71.15	$71.10
Purchase #5	$60.61	8.391%	$65.6958	$65.70	$65.70	$65.70
Purchase #6	$52.56	13.612%	$59.7145	$59.71	$59.70	$59.70
Purchase #7	$108.26	4.286%	$112.9	$112.90	$112.90	$112.90
7 purchase totals =	$459.37		$502.2012	$502.20	$502.20	$502.10