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	$82.37	10.505%	$91.023	$91.02	$91.00	$91.00
Purchase #2	$191.33	8.779%	$208.1269	$208.13	$208.15	$208.10
Purchase #3	$165.30	3.727%	$171.4607	$171.46	$171.45	$171.50
Purchase #4	$130.92	10.813%	$145.0764	$145.08	$145.10	$145.10
Purchase #5	$233.87	4.142%	$243.5569	$243.56	$243.55	$243.60
Purchase #6	$163.60	9.348%	$178.8933	$178.89	$178.90	$178.90
Purchase #7	$7.77	13.854%	$8.8465	$8.85	$8.85	$8.80
7 purchase totals =	$975.16		$1,046.9837	$1,046.99	$1,047.00	$1,047.00