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	$41.67	9.526%	$45.6395	$45.64	$45.65	$45.60
Purchase #2	$191.72	12.376%	$215.4473	$215.45	$215.45	$215.40
Purchase #3	$207.78	9.690%	$227.9139	$227.91	$227.90	$227.90
Purchase #4	$124.59	10.198%	$137.2957	$137.30	$137.30	$137.30
Purchase #5	$147.38	12.233%	$165.409	$165.41	$165.40	$165.40
Purchase #6	$135.40	7.165%	$145.1014	$145.10	$145.10	$145.10
Purchase #7	$12.41	6.254%	$13.1861	$13.19	$13.20	$13.20
7 purchase totals =	$860.95		$949.9929	$950.00	$950.00	$949.90