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	$130.70	11.364%	$145.5527	$145.55	$145.55	$145.60
Purchase #2	$117.92	13.583%	$133.9371	$133.94	$133.95	$133.90
Purchase #3	$158.89	6.724%	$169.5738	$169.57	$169.55	$169.60
Purchase #4	$181.77	5.226%	$191.2693	$191.27	$191.25	$191.30
Purchase #5	$241.98	5.558%	$255.4292	$255.43	$255.45	$255.40
Purchase #6	$61.92	9.366%	$67.7194	$67.72	$67.70	$67.70
Purchase #7	$57.69	4.579%	$60.3316	$60.33	$60.35	$60.30
7 purchase totals =	$950.87		$1,023.8131	$1,023.81	$1,023.80	$1,023.80