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	$168.57	13.308%	$191.0033	$191.00	$191.00	$191.00
Purchase #2	$150.51	9.568%	$164.9108	$164.91	$164.90	$164.90
Purchase #3	$96.35	10.710%	$106.6691	$106.67	$106.65	$106.70
Purchase #4	$206.94	7.725%	$222.9261	$222.93	$222.95	$222.90
Purchase #5	$94.80	11.346%	$105.556	$105.56	$105.55	$105.60
Purchase #6	$77.51	5.152%	$81.5033	$81.50	$81.50	$81.50
Purchase #7	$195.51	13.818%	$222.5256	$222.53	$222.55	$222.50
7 purchase totals =	$990.19		$1,095.0942	$1,095.10	$1,095.10	$1,095.10