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	$112.89	9.604%	$123.732	$123.73	$123.75	$123.70
Purchase #2	$93.48	4.832%	$97.997	$98.00	$98.00	$98.00
Purchase #3	$189.39	13.662%	$215.2645	$215.26	$215.25	$215.30
Purchase #4	$37.94	10.210%	$41.8137	$41.81	$41.80	$41.80
Purchase #5	$111.83	4.839%	$117.2415	$117.24	$117.25	$117.20
Purchase #6	$79.82	7.460%	$85.7746	$85.77	$85.75	$85.80
Purchase #7	$28.76	10.198%	$31.6929	$31.69	$31.70	$31.70
7 purchase totals =	$654.11		$713.5162	$713.50	$713.50	$713.50