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	$150.53	10.156%	$165.8178	$165.82	$165.80	$165.80
Purchase #2	$68.25	5.533%	$72.0263	$72.03	$72.05	$72.00
Purchase #3	$52.42	4.402%	$54.7275	$54.73	$54.75	$54.70
Purchase #4	$156.86	7.309%	$168.3249	$168.32	$168.30	$168.30
Purchase #5	$57.36	9.453%	$62.7822	$62.78	$62.80	$62.80
Purchase #6	$193.78	11.243%	$215.5667	$215.57	$215.55	$215.60
Purchase #7	$181.85	6.749%	$194.1231	$194.12	$194.10	$194.10
7 purchase totals =	$861.05		$933.3685	$933.37	$933.35	$933.30