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	$61.86	13.836%	$70.4189	$70.42	$70.40	$70.40
Purchase #2	$212.55	9.810%	$233.4012	$233.40	$233.40	$233.40
Purchase #3	$171.43	5.462%	$180.7935	$180.79	$180.80	$180.80
Purchase #4	$194.87	10.374%	$215.0858	$215.09	$215.10	$215.10
Purchase #5	$110.61	3.632%	$114.6274	$114.63	$114.65	$114.60
Purchase #6	$213.49	4.617%	$223.3468	$223.35	$223.35	$223.30
Purchase #7	$49.80	10.323%	$54.9409	$54.94	$54.95	$54.90
7 purchase totals =	$1,014.61		$1,092.6145	$1,092.62	$1,092.65	$1,092.50