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	$81.65	10.751%	$90.4282	$90.43	$90.45	$90.40
Purchase #2	$6.45	7.139%	$6.9105	$6.91	$6.90	$6.90
Purchase #3	$139.85	4.572%	$146.2439	$146.24	$146.25	$146.20
Purchase #4	$181.57	4.428%	$189.6099	$189.61	$189.60	$189.60
Purchase #5	$237.29	12.754%	$267.554	$267.55	$267.55	$267.60
Purchase #6	$194.66	10.780%	$215.6443	$215.64	$215.65	$215.60
Purchase #7	$247.45	8.601%	$268.7332	$268.73	$268.75	$268.70
7 purchase totals =	$1,088.92		$1,185.1240	$1,185.11	$1,185.15	$1,185.00