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	$105.90	10.374%	$116.8861	$116.89	$116.90	$116.90
Purchase #2	$162.54	10.413%	$179.4653	$179.47	$179.45	$179.50
Purchase #3	$41.53	4.334%	$43.3299	$43.33	$43.35	$43.30
Purchase #4	$39.66	4.194%	$41.3233	$41.32	$41.30	$41.30
Purchase #5	$65.76	3.796%	$68.2562	$68.26	$68.25	$68.30
Purchase #6	$192.94	3.616%	$199.9167	$199.92	$199.90	$199.90
Purchase #7	$49.32	10.162%	$54.3319	$54.33	$54.35	$54.30
7 purchase totals =	$657.65		$703.5094	$703.52	$703.50	$703.50