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	$67.88	6.525%	$72.3092	$72.31	$72.30	$72.30
Purchase #2	$246.27	3.697%	$255.3746	$255.37	$255.35	$255.40
Purchase #3	$66.98	12.856%	$75.5909	$75.59	$75.60	$75.60
Purchase #4	$228.72	7.124%	$245.014	$245.01	$245.00	$245.00
Purchase #5	$85.32	4.422%	$89.0929	$89.09	$89.10	$89.10
Purchase #6	$69.41	10.562%	$76.7411	$76.74	$76.75	$76.70
Purchase #7	$196.43	6.419%	$209.0388	$209.04	$209.05	$209.00
7 purchase totals =	$961.01		$1,023.1615	$1,023.15	$1,023.15	$1,023.10