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	$41.91	4.120%	$43.6367	$43.64	$43.65	$43.60
Purchase #2	$33.78	7.270%	$36.2358	$36.24	$36.25	$36.20
Purchase #3	$112.56	7.365%	$120.85	$120.85	$120.85	$120.90
Purchase #4	$241.72	3.590%	$250.3977	$250.40	$250.40	$250.40
Purchase #5	$55.98	4.151%	$58.3037	$58.30	$58.30	$58.30
Purchase #6	$130.45	6.846%	$139.3806	$139.38	$139.40	$139.40
Purchase #7	$104.99	6.752%	$112.0789	$112.08	$112.10	$112.10
7 purchase totals =	$721.39		$760.8834	$760.89	$760.95	$760.90