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	$135.88	6.820%	$145.147	$145.15	$145.15	$145.10
Purchase #2	$100.50	5.510%	$106.0376	$106.04	$106.05	$106.00
Purchase #3	$124.45	5.156%	$130.8666	$130.87	$130.85	$130.90
Purchase #4	$55.87	7.343%	$59.9725	$59.97	$59.95	$60.00
Purchase #5	$176.82	5.158%	$185.9404	$185.94	$185.95	$185.90
Purchase #6	$202.34	5.654%	$213.7803	$213.78	$213.80	$213.80
Purchase #7	$162.83	7.302%	$174.7198	$174.72	$174.70	$174.70
7 purchase totals =	$958.69		$1,016.4642	$1,016.47	$1,016.45	$1,016.40