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	$145.47	7.403%	$156.2391	$156.24	$156.25	$156.20
Purchase #2	$220.37	10.501%	$243.5111	$243.51	$243.50	$243.50
Purchase #3	$100.78	4.456%	$105.2708	$105.27	$105.25	$105.30
Purchase #4	$127.53	3.268%	$131.6977	$131.70	$131.70	$131.70
Purchase #5	$189.78	6.576%	$202.2599	$202.26	$202.25	$202.30
Purchase #6	$160.63	13.183%	$181.8059	$181.81	$181.80	$181.80
Purchase #7	$157.58	8.605%	$171.1398	$171.14	$171.15	$171.10
7 purchase totals =	$1,102.14		$1,191.9243	$1,191.93	$1,191.90	$1,191.90