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	$102.66	12.150%	$115.1332	$115.13	$115.15	$115.10
Purchase #2	$101.37	8.623%	$110.1111	$110.11	$110.10	$110.10
Purchase #3	$108.76	3.629%	$112.7069	$112.71	$112.70	$112.70
Purchase #4	$54.98	13.779%	$62.5557	$62.56	$62.55	$62.60
Purchase #5	$156.85	7.359%	$168.3926	$168.39	$168.40	$168.40
Purchase #6	$209.42	7.661%	$225.4637	$225.46	$225.45	$225.50
Purchase #7	$188.61	11.780%	$210.8283	$210.83	$210.85	$210.80
7 purchase totals =	$922.65		$1,005.1915	$1,005.19	$1,005.20	$1,005.20