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	$124.73	3.651%	$129.2839	$129.28	$129.30	$129.30
Purchase #2	$172.61	7.234%	$185.0966	$185.10	$185.10	$185.10
Purchase #3	$143.86	10.429%	$158.8632	$158.86	$158.85	$158.90
Purchase #4	$131.99	9.424%	$144.4287	$144.43	$144.45	$144.40
Purchase #5	$224.97	8.457%	$243.9957	$244.00	$244.00	$244.00
Purchase #6	$140.79	8.270%	$152.4333	$152.43	$152.45	$152.40
Purchase #7	$80.89	10.720%	$89.5614	$89.56	$89.55	$89.60
7 purchase totals =	$1,019.84		$1,103.6628	$1,103.66	$1,103.70	$1,103.70