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	$105.38	6.212%	$111.9262	$111.93	$111.95	$111.90
Purchase #2	$224.50	9.459%	$245.7355	$245.74	$245.75	$245.70
Purchase #3	$72.91	12.834%	$82.2673	$82.27	$82.25	$82.30
Purchase #4	$174.54	12.522%	$196.3959	$196.40	$196.40	$196.40
Purchase #5	$211.80	7.505%	$227.6956	$227.70	$227.70	$227.70
Purchase #6	$202.37	6.618%	$215.7628	$215.76	$215.75	$215.80
Purchase #7	$140.47	9.366%	$153.6264	$153.63	$153.65	$153.60
7 purchase totals =	$1,131.97		$1,233.4097	$1,233.43	$1,233.45	$1,233.40