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	$219.93	11.655%	$245.5628	$245.56	$245.55	$245.60
Purchase #2	$49.78	10.695%	$55.104	$55.10	$55.10	$55.10
Purchase #3	$156.76	11.216%	$174.3422	$174.34	$174.35	$174.30
Purchase #4	$31.83	3.167%	$32.8381	$32.84	$32.85	$32.80
Purchase #5	$242.82	9.542%	$265.9899	$265.99	$266.00	$266.00
Purchase #6	$164.78	4.150%	$171.6184	$171.62	$171.60	$171.60
Purchase #7	$123.46	9.471%	$135.1529	$135.15	$135.15	$135.20
7 purchase totals =	$989.36		$1,080.6083	$1,080.60	$1,080.60	$1,080.60