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	$234.89	10.391%	$259.2974	$259.30	$259.30	$259.30
Purchase #2	$98.38	13.390%	$111.5531	$111.55	$111.55	$111.60
Purchase #3	$55.65	12.791%	$62.7682	$62.77	$62.75	$62.80
Purchase #4	$226.59	6.285%	$240.8312	$240.83	$240.85	$240.80
Purchase #5	$222.54	10.567%	$246.0558	$246.06	$246.05	$246.10
Purchase #6	$53.30	8.614%	$57.8913	$57.89	$57.90	$57.90
Purchase #7	$156.70	9.225%	$171.1556	$171.16	$171.15	$171.20
7 purchase totals =	$1,048.05		$1,149.5526	$1,149.56	$1,149.55	$1,149.70