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	$238.41	12.216%	$267.5342	$267.53	$267.55	$267.50
Purchase #2	$240.25	11.545%	$267.9869	$267.99	$268.00	$268.00
Purchase #3	$110.33	12.236%	$123.83	$123.83	$123.85	$123.80
Purchase #4	$101.43	7.835%	$109.377	$109.38	$109.40	$109.40
Purchase #5	$66.99	8.150%	$72.4497	$72.45	$72.45	$72.40
Purchase #6	$154.49	3.823%	$160.3962	$160.40	$160.40	$160.40
Purchase #7	$97.66	8.179%	$105.6476	$105.65	$105.65	$105.60
7 purchase totals =	$1,009.56		$1,107.2216	$1,107.23	$1,107.30	$1,107.10