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	$224.92	3.838%	$233.5524	$233.55	$233.55	$233.60
Purchase #2	$211.83	3.609%	$219.4749	$219.47	$219.45	$219.50
Purchase #3	$61.91	13.174%	$70.066	$70.07	$70.05	$70.10
Purchase #4	$100.77	4.527%	$105.3319	$105.33	$105.35	$105.30
Purchase #5	$232.95	12.123%	$261.1905	$261.19	$261.20	$261.20
Purchase #6	$36.30	6.272%	$38.5767	$38.58	$38.60	$38.60
Purchase #7	$119.60	7.138%	$128.137	$128.14	$128.15	$128.10
7 purchase totals =	$988.28		$1,056.3294	$1,056.33	$1,056.35	$1,056.40