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	$139.64	3.293%	$144.2383	$144.24	$144.25	$144.20
Purchase #2	$68.64	5.616%	$72.4948	$72.49	$72.50	$72.50
Purchase #3	$181.74	5.370%	$191.4994	$191.50	$191.50	$191.50
Purchase #4	$68.32	5.865%	$72.327	$72.33	$72.35	$72.30
Purchase #5	$119.95	5.552%	$126.6096	$126.61	$126.60	$126.60
Purchase #6	$33.93	7.468%	$36.4639	$36.46	$36.45	$36.50
Purchase #7	$141.58	8.746%	$153.9626	$153.96	$153.95	$154.00
7 purchase totals =	$753.80		$797.5956	$797.59	$797.60	$797.60