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	$225.38	10.353%	$248.7136	$248.71	$248.70	$248.70
Purchase #2	$135.75	4.703%	$142.1343	$142.13	$142.15	$142.10
Purchase #3	$83.27	7.365%	$89.4028	$89.40	$89.40	$89.40
Purchase #4	$89.77	11.663%	$100.2399	$100.24	$100.25	$100.20
Purchase #5	$34.81	3.697%	$36.0969	$36.10	$36.10	$36.10
Purchase #6	$219.45	9.476%	$240.2451	$240.25	$240.25	$240.20
Purchase #7	$96.90	4.429%	$101.1917	$101.19	$101.20	$101.20
7 purchase totals =	$885.33		$958.0243	$958.02	$958.05	$957.90