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	$169.59	5.118%	$178.2696	$178.27	$178.25	$178.30
Purchase #2	$41.54	5.157%	$43.6822	$43.68	$43.70	$43.70
Purchase #3	$50.82	5.771%	$53.7528	$53.75	$53.75	$53.80
Purchase #4	$38.69	3.109%	$39.8929	$39.89	$39.90	$39.90
Purchase #5	$45.47	8.339%	$49.2617	$49.26	$49.25	$49.30
Purchase #6	$203.66	8.780%	$221.5413	$221.54	$221.55	$221.50
Purchase #7	$84.37	7.712%	$90.8766	$90.88	$90.90	$90.90
7 purchase totals =	$634.14		$677.2771	$677.27	$677.30	$677.40