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	$103.61	5.719%	$109.5355	$109.54	$109.55	$109.50
Purchase #2	$187.74	5.872%	$198.7641	$198.76	$198.75	$198.80
Purchase #3	$28.65	9.618%	$31.4056	$31.41	$31.40	$31.40
Purchase #4	$73.63	6.461%	$78.3872	$78.39	$78.40	$78.40
Purchase #5	$203.93	10.396%	$225.1306	$225.13	$225.15	$225.10
Purchase #6	$139.87	13.440%	$158.6685	$158.67	$158.65	$158.70
Purchase #7	$143.73	6.751%	$153.4332	$153.43	$153.45	$153.40
7 purchase totals =	$881.16		$955.3247	$955.33	$955.35	$955.30