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	$50.75	3.117%	$52.3319	$52.33	$52.35	$52.30
Purchase #2	$90.88	8.817%	$98.8929	$98.89	$98.90	$98.90
Purchase #3	$153.75	7.149%	$164.7416	$164.74	$164.75	$164.70
Purchase #4	$209.80	7.443%	$225.4154	$225.42	$225.40	$225.40
Purchase #5	$96.34	5.724%	$101.8545	$101.85	$101.85	$101.90
Purchase #6	$120.56	6.519%	$128.4193	$128.42	$128.40	$128.40
Purchase #7	$49.92	5.415%	$52.6232	$52.62	$52.60	$52.60
7 purchase totals =	$772.00		$824.2788	$824.27	$824.25	$824.20