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	$179.72	9.234%	$196.3153	$196.32	$196.30	$196.30
Purchase #2	$209.85	6.257%	$222.9803	$222.98	$223.00	$223.00
Purchase #3	$84.36	6.661%	$89.9792	$89.98	$90.00	$90.00
Purchase #4	$202.34	6.474%	$215.4395	$215.44	$215.45	$215.40
Purchase #5	$188.58	9.351%	$206.2141	$206.21	$206.20	$206.20
Purchase #6	$105.58	3.669%	$109.4537	$109.45	$109.45	$109.50
Purchase #7	$34.58	5.384%	$36.4418	$36.44	$36.45	$36.40
7 purchase totals =	$1,005.01		$1,076.8239	$1,076.82	$1,076.85	$1,076.80