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	$141.60	5.390%	$149.2322	$149.23	$149.25	$149.20
Purchase #2	$99.41	8.661%	$108.0199	$108.02	$108.00	$108.00
Purchase #3	$217.98	11.719%	$243.5251	$243.53	$243.55	$243.50
Purchase #4	$27.28	3.801%	$28.3169	$28.32	$28.30	$28.30
Purchase #5	$169.43	7.176%	$181.5883	$181.59	$181.60	$181.60
Purchase #6	$29.93	13.582%	$33.9951	$34.00	$34.00	$34.00
Purchase #7	$240.43	9.399%	$263.028	$263.03	$263.05	$263.00
7 purchase totals =	$926.06		$1,007.7055	$1,007.72	$1,007.75	$1,007.60