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	$180.90	10.817%	$200.468	$200.47	$200.45	$200.50
Purchase #2	$221.55	10.638%	$245.1185	$245.12	$245.10	$245.10
Purchase #3	$49.32	8.217%	$53.3726	$53.37	$53.35	$53.40
Purchase #4	$225.41	3.859%	$234.1086	$234.11	$234.10	$234.10
Purchase #5	$63.90	3.376%	$66.0573	$66.06	$66.05	$66.10
Purchase #6	$199.90	4.581%	$209.0574	$209.06	$209.05	$209.10
Purchase #7	$131.43	10.242%	$144.8911	$144.89	$144.90	$144.90
7 purchase totals =	$1,072.41		$1,153.0735	$1,153.08	$1,153.00	$1,153.20