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	$203.95	13.647%	$231.7831	$231.78	$231.80	$231.80
Purchase #2	$42.46	5.167%	$44.6539	$44.65	$44.65	$44.70
Purchase #3	$39.34	7.555%	$42.3121	$42.31	$42.30	$42.30
Purchase #4	$91.50	13.308%	$103.6768	$103.68	$103.70	$103.70
Purchase #5	$125.70	13.383%	$142.5224	$142.52	$142.50	$142.50
Purchase #6	$179.85	6.705%	$191.9089	$191.91	$191.90	$191.90
Purchase #7	$243.69	6.717%	$260.0587	$260.06	$260.05	$260.10
7 purchase totals =	$926.49		$1,016.9159	$1,016.91	$1,016.90	$1,017.00