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	$188.54	8.360%	$204.3019	$204.30	$204.30	$204.30
Purchase #2	$219.83	9.528%	$240.7754	$240.78	$240.80	$240.80
Purchase #3	$19.73	4.572%	$20.6321	$20.63	$20.65	$20.60
Purchase #4	$89.87	5.700%	$94.9926	$94.99	$95.00	$95.00
Purchase #5	$75.60	6.392%	$80.4324	$80.43	$80.45	$80.40
Purchase #6	$188.95	3.850%	$196.2246	$196.22	$196.20	$196.20
Purchase #7	$232.63	11.284%	$258.88	$258.88	$258.90	$258.90
7 purchase totals =	$1,015.15		$1,096.2390	$1,096.23	$1,096.30	$1,096.20