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	$112.59	5.152%	$118.3906	$118.39	$118.40	$118.40
Purchase #2	$79.58	3.168%	$82.1011	$82.10	$82.10	$82.10
Purchase #3	$61.98	3.862%	$64.3737	$64.37	$64.35	$64.40
Purchase #4	$215.72	5.554%	$227.7011	$227.70	$227.70	$227.70
Purchase #5	$225.78	12.248%	$253.4335	$253.43	$253.45	$253.40
Purchase #6	$97.33	7.174%	$104.3125	$104.31	$104.30	$104.30
Purchase #7	$223.62	11.458%	$249.2424	$249.24	$249.25	$249.20
7 purchase totals =	$1,016.60		$1,099.5549	$1,099.54	$1,099.55	$1,099.50