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	$82.27	8.489%	$89.2539	$89.25	$89.25	$89.30
Purchase #2	$125.82	5.793%	$133.1088	$133.11	$133.10	$133.10
Purchase #3	$93.45	13.844%	$106.3872	$106.39	$106.40	$106.40
Purchase #4	$95.78	7.165%	$102.6426	$102.64	$102.65	$102.60
Purchase #5	$58.40	6.648%	$62.2824	$62.28	$62.30	$62.30
Purchase #6	$196.93	13.806%	$224.1182	$224.12	$224.10	$224.10
Purchase #7	$13.64	4.405%	$14.2408	$14.24	$14.25	$14.20
7 purchase totals =	$666.29		$732.0339	$732.03	$732.05	$732.00