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	$134.54	13.658%	$152.9155	$152.92	$152.90	$152.90
Purchase #2	$183.37	5.449%	$193.3618	$193.36	$193.35	$193.40
Purchase #3	$80.32	4.396%	$83.8509	$83.85	$83.85	$83.90
Purchase #4	$146.51	4.127%	$152.5565	$152.56	$152.55	$152.60
Purchase #5	$246.38	7.623%	$265.1615	$265.16	$265.15	$265.20
Purchase #6	$185.79	8.106%	$200.8501	$200.85	$200.85	$200.90
Purchase #7	$45.46	9.538%	$49.796	$49.80	$49.80	$49.80
7 purchase totals =	$1,022.37		$1,098.4923	$1,098.50	$1,098.45	$1,098.70