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	$186.35	4.711%	$195.1289	$195.13	$195.15	$195.10
Purchase #2	$50.78	7.108%	$54.3894	$54.39	$54.40	$54.40
Purchase #3	$116.81	8.796%	$127.0846	$127.08	$127.10	$127.10
Purchase #4	$79.70	3.263%	$82.3006	$82.30	$82.30	$82.30
Purchase #5	$86.50	5.549%	$91.2999	$91.30	$91.30	$91.30
Purchase #6	$120.68	13.854%	$137.399	$137.40	$137.40	$137.40
Purchase #7	$118.64	7.341%	$127.3494	$127.35	$127.35	$127.30
7 purchase totals =	$759.46		$814.9518	$814.95	$815.00	$814.90